[Flang][Windows] Don't try to run Unix-specific tests on Windows (#392)

Some of these recently added tests call functions only available in
POSIX, and also assume that the linker accepts -fopenmp. These won't
work on Windows, so we shouldn't attempt to build or run them there.

Author: DavidTruby

Fortran/cray/OpenMP/CMakeLists.txt

@@ -1,3 +1,3 @@
-if(OPENMP_FOUND)
+if(OPENMP_FOUND AND NOT WIN32)
   add_subdirectory(5.0)
 endif()