[cmake] Assume we always have C++11 threads.

  - Threads support is needed for HPCOM CPP runtime tests.
  - It is a fair assumption for now. If it needs to be checked and enabled
    we will do that later.

OMCompiler/SimulationRuntime/cpp/Core/CMakeLists.txt

@@ -8,7 +8,7 @@ set(Boost_INCLUDE_ ".")
 set(Boost_LIBS_ ".")
 set(LAPACK_LIBS_ ".")
 set(LAPACK_LIBRARIES_ "-llapack -lblas")
-set(SYSTEM_CFLAGS ${SYSTEM_CFLAGS} "-DOMC_BUILD -fPIC")
+set(SYSTEM_CFLAGS ${SYSTEM_CFLAGS} "-DOMC_BUILD -fPIC -DUSE_THREAD")
 
 configure_file(Modelica/ModelicaLibraryConfig_gcc.inc.in ${CMAKE_CURRENT_BINARY_DIR}/ModelicaLibraryConfig_gcc.inc)
 configure_file(Modelica/ModelicaConfig_gcc.inc.in ${CMAKE_CURRENT_BINARY_DIR}/ModelicaConfig_gcc.inc)