cmake HAVE_C11 examples

ComputationalBiomechanicsLab/opensim-creator third_party/OpenBLAS/cmake/system_check.cmake :143 

CHECK_INCLUDE_FILE("stdatomic.h" HAVE_C11)

OpenMathLib/OpenBLAS cmake/system_check.cmake :159 

CHECK_INCLUDE_FILE("stdatomic.h" HAVE_C11)