[Flang][Runtime][OpenMP][AMDGPU] Revert part of #152631 causing regression for amdgpu

When modifying the PR during review I made a minor alteration that I thought made sense,
but after further testing doesn't seem to. So, in this commit I regress the offending bit
of code.

Author: agozillon

flang/include/flang/Runtime/freestanding-tools.h

@@ -63,8 +63,7 @@
 #define STD_TOUPPER_UNSUPPORTED 1
 #endif
 
-#if defined(OMP_OFFLOAD_BUILD) && defined(OMP_NOHOST_BUILD) && \
-    defined(__clang__)
+#if defined(OMP_OFFLOAD_BUILD) && defined(__clang__)
 #define STD_FILL_N_UNSUPPORTED 1
 #define STD_MEMSET_USE_BUILTIN 1
 #define STD_MEMSET_UNSUPPORTED 1