[WIP] Enable regions again. (#64688)

* Enable regions again.

* disable regions for MacOS for now.

* disable for NativeAOT for now

Author: mangod9

src/coreclr/gc/gcpriv.h

@@ -51,8 +51,8 @@ inline void FATAL_GC_ERROR()
 //
 // This means any empty regions can be freely used for any generation. For
 // Server GC we will balance regions between heaps.
-// For now disable regions outside of StandAlone GC builds
-#if defined (HOST_64BIT) && defined (BUILD_AS_STANDALONE)
+// For now disable regions for StandAlone GC, NativeAOT and MacOS builds
+#if defined (HOST_64BIT) && !defined (BUILD_AS_STANDALONE) && !defined(__APPLE__) && !defined(FEATURE_REDHAWK)
 #define USE_REGIONS
 #endif //HOST_64BIT && BUILD_AS_STANDALONE