I assume that you are trying to build on a Mac.  If so, you need to add openmodelica to your sources so that it is available. 
See the first step of this:  Mac Instructions 

I am trying to build the openmodelica using the source package in the macports repository.
I did it a lot of times successfully.
In this time the package is missing in the macports repository.
If you try to use the port search command as the following:
sudo ports search --name --line --glob '*modelica*' the result is an empty list.
Last week, the command port install openmodelica-devel +libraries +clang works, that means, the source package is in the macports repository, but does not work properly, the installation fails in the last step when the procedure invoke the C compiler to make a compilation test.(Xcode and gcc44 were installed properly)
Maybe the source package was removed from the macports repository to fix the installation procedure.
I like to use this procedure because I feel more sure to uninstall all the elements if it necessary.
If we can find when the source will be available in the macports repository, I can wait until that.

I have never seen OpenModelica available in the Macports.org repository.  I have been building it from source on my Mac using Macports for a long time.  The way I have always done it, is to follow the instructions above.  What these instructions do is first require you to add openmodelica as a valid source to your macports installation:

echo rsync://build.openmodelica.org/macports/ >> /opt/local/etc/macports/sources.conf # assuming you installed into /opt/local

Note, that this only has to happen once for each installation of Macports. sources.conf just tells macports where to search for packages (binary and source)
Then, when you do:

sudo port install openmodelica-devel

it will search both macports and openmodelica to find the source code and use it to build.

It would be possible for someone to add the source to the macports.org repository but I am not aware of it ever happening before (If so, I could have missed it)

Yes desh, you are right. I forgot to run the first command in my last installation. Thank you.
I run it and the command add the following line into source.conf
rsync://build.openmodelica.org/macports/
Now my problem is for more than one month I receive en error at the end of the installation.
How can I select another version for build the openmodelica in my mac?

I run the mac procedure for install openmodelica and the installation fails.
The log points to this errors.
:info:build -- The C compiler identification is Clang 3.8.1
:info:build -- The CXX compiler identification is Clang 3.8.1
:info:build -- Check for working C compiler: /opt/local/bin/clang-mp-3.8
:info:build autoreconf: Entering directory `.'
:info:build autoreconf: configure.ac: not using Gettext
:info:build -- Check for working C compiler: /opt/local/bin/clang-mp-3.8 -- broken
:info:build CMake Error at /opt/local/share/cmake-3.7/Modules/CMakeTestCCompiler.cmake:51 (message):
:info:build   The C compiler "/opt/local/bin/clang-mp-3.8" is not able to compile a
:info:build   simple test program.
:info:build
:info:build   It fails with the following output:
:info:build
:info:build    Change Dir: /opt/local/var/macports/build/_opt_local_var_macports_sources_build.openmodelica.org_macports_lang_openmodelica-devel/openmodelica-devel/work/openmodelica_1.12.0~dev-140-g1db5844/OMCompiler/3rdParty/FMIL/build/CMakeFiles/CMakeTmp
and the following
:info:build   Linking C executable cmTC_6a2fa
:info:build
:info:build   /opt/local/bin/cmake -E cmake_link_script
:info:build   CMakeFiles/cmTC_6a2fa.dir/link.txt --verbose=1
:info:build
:info:build   /opt/local/bin/clang-mp-3.8 -pipe -Os -arch x86_64 -fno-stack-protector
:info:build   -isysroot
:info:build   /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk
:info:build   -mmacosx-version-min=10.12 -Wl,-search_paths_first
:info:build   -Wl,-headerpad_max_install_names -Wl,-undefined -Wl,dynamic_lookup
:info:build   CMakeFiles/cmTC_6a2fa.dir/testCCompiler.c.o -o cmTC_6a2fa
:info:build
:info:build   ld: unexpected token: !tapi-tbd-v2 file
:info:build   '/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk/usr/lib/libSystem.tbd'
:info:build   for architecture x86_64
:info:build
:info:build   clang: error: linker command failed with exit code 1 (use -v to see
:info:build   invocation)
:info:build
:info:build   CMakeFiles/cmTC_6a2fa.dir/build.make:97: recipe for target 'cmTC_6a2fa'
:info:build   failed
:info:build
:info:build   gmake[4]: *** [cmTC_6a2fa] Error 1
:info:build
:info:build   gmake[4]: Leaving directory
:info:build   '/opt/local/var/macports/build/_opt_local_var_macports_sources_build.openmodelica.org_macports_lang_openmodelica-devel/openmodelica-devel/work/openmodelica_1.12.0~dev-140-g1db5844/OMCompiler/3rdParty/FMIL/build/CMakeFiles/CMakeTmp'
:info:build
:info:build
:info:build   Makefile:126: recipe for target 'cmTC_6a2fa/fast' failed
:info:build
:info:build   gmake[3]: *** [cmTC_6a2fa/fast] Error 2
:info:build
:info:build   gmake[3]: Leaving directory
:info:build   '/opt/local/var/macports/build/_opt_local_var_macports_sources_build.openmodelica.org_macports_lang_openmodelica-devel/openmodelica-devel/work/openmodelica_1.12.0~dev-140-g1db5844/OMCompiler/3rdParty/FMIL/build/CMakeFiles/CMakeTmp'
:info:build
:info:build
:info:build   
:info:build
:info:build   
:info:build
:info:build   CMake will not be able to correctly generate this project.
:info:build Call Stack (most recent call first):
:info:build   CMakeLists.txt:23 (project)
The compilers do not works properly in the installation process.

I run the mac procedure for install openmodelica and the installation fails.
The log points to this errors.
:info:build -- The C compiler identification is Clang 3.8.1
:info:build -- The CXX compiler identification is Clang 3.8.1
:info:build -- Check for working C compiler: /opt/local/bin/clang-mp-3.8
:info:build autoreconf: Entering directory `.'
:info:build autoreconf: configure.ac: not using Gettext
:info:build -- Check for working C compiler: /opt/local/bin/clang-mp-3.8 -- broken
:info:build CMake Error at /opt/local/share/cmake-3.7/Modules/CMakeTestCCompiler.cmake:51 (message):
:info:build   The C compiler "/opt/local/bin/clang-mp-3.8" is not able to compile a
:info:build   simple test program.
:info:build
:info:build   It fails with the following output:
:info:build
:info:build    Change Dir: /opt/local/var/macports/build/_opt_local_var_macports_sources_build.openmodelica.org_macports_lang_openmodelica-devel/openmodelica-devel/work/openmodelica_1.12.0~dev-140-g1db5844/OMCompiler/3rdParty/FMIL/build/CMakeFiles/CMakeTmp
and the following
:info:build   Linking C executable cmTC_6a2fa
:info:build
:info:build   /opt/local/bin/cmake -E cmake_link_script
:info:build   CMakeFiles/cmTC_6a2fa.dir/link.txt --verbose=1
:info:build
:info:build   /opt/local/bin/clang-mp-3.8 -pipe -Os -arch x86_64 -fno-stack-protector
:info:build   -isysroot
:info:build   /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk
:info:build   -mmacosx-version-min=10.12 -Wl,-search_paths_first
:info:build   -Wl,-headerpad_max_install_names -Wl,-undefined -Wl,dynamic_lookup
:info:build   CMakeFiles/cmTC_6a2fa.dir/testCCompiler.c.o -o cmTC_6a2fa
:info:build
:info:build   ld: unexpected token: !tapi-tbd-v2 file
:info:build   '/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk/usr/lib/libSystem.tbd'
:info:build   for architecture x86_64
:info:build
:info:build   clang: error: linker command failed with exit code 1 (use -v to see
:info:build   invocation)
:info:build
:info:build   CMakeFiles/cmTC_6a2fa.dir/build.make:97: recipe for target 'cmTC_6a2fa'
:info:build   failed
:info:build
:info:build   gmake[4]: *** [cmTC_6a2fa] Error 1
:info:build
:info:build   gmake[4]: Leaving directory
:info:build   '/opt/local/var/macports/build/_opt_local_var_macports_sources_build.openmodelica.org_macports_lang_openmodelica-devel/openmodelica-devel/work/openmodelica_1.12.0~dev-140-g1db5844/OMCompiler/3rdParty/FMIL/build/CMakeFiles/CMakeTmp'
:info:build
:info:build
:info:build   Makefile:126: recipe for target 'cmTC_6a2fa/fast' failed
:info:build
:info:build   gmake[3]: *** [cmTC_6a2fa/fast] Error 2
:info:build
:info:build   gmake[3]: Leaving directory
:info:build   '/opt/local/var/macports/build/_opt_local_var_macports_sources_build.openmodelica.org_macports_lang_openmodelica-devel/openmodelica-devel/work/openmodelica_1.12.0~dev-140-g1db5844/OMCompiler/3rdParty/FMIL/build/CMakeFiles/CMakeTmp'
:info:build
:info:build
:info:build   
:info:build
:info:build   
:info:build
:info:build   CMake will not be able to correctly generate this project.
:info:build Call Stack (most recent call first):
:info:build   CMakeLists.txt:23 (project)
The compilers do not works properly in the installation process.

It looks to me like some other part of your install of macports is missing.  Maybe +clang is trying to select non-installed clang compiler. 
I think that the default build settings now should work OK.  So, I would just try this:

port install openmodelica-devel +libraries

You do need to have Xcode installed for most ports, including openmodelica, to build (while binary only ports can install without it)

Thank you!!
The installation pass successfully but the application is not stable.
After some examples running it crash.
We need to wait until the application becomes stable.