Avoid having OpenMP as a dependency of the whole O2 (#16047)

Author: ktf

Utilities/rANS/CMakeLists.txt

@@ -44,7 +44,7 @@ if(${RANS_LOG_PROCESSED_DATA})
 endif()
 if (OpenMP_CXX_FOUND AND ( NOT APPLE ) )
     target_compile_definitions(${LIBRANS} INTERFACE RANS_OPENMP)
-    target_link_libraries(${LIBRANS} INTERFACE OpenMP::OpenMP_CXX)
+    target_compile_options(${LIBRANS} INTERFACE $<$<COMPILE_LANGUAGE:CXX>:-fopenmp-simd>)
 endif()
 if(${ENABLE_VTUNE_PROFILER})
   target_compile_definitions(${LIBRANS} INTERFACE ENABLE_VTUNE_PROFILER)

Utilities/rANS/include/rANS/internal/containers/DenseHistogram.h

@@ -33,11 +33,6 @@
 #ifdef RANS_SIMD
 #include "rANS/internal/common/simdops.h"
 #include "rANS/internal/common/simdtypes.h"
-
-#ifdef RANS_OPENMP
-#include <omp.h>
-#endif
-
 #endif /* RANS_SIMD */
 
 namespace o2::rans