rts: assert pointer is indeed heap allocated in Bdescr()

This commit adds an assertion to Bdescr() to assert the pointer is
indeed heap allocated. This is useful to rule out RTS bugs that
attempt to access non-existent block descriptor of a static closure, #24492
being one such example.

rts/include/rts/storage/Block.h

@@ -10,6 +10,10 @@
 
 #include "ghcconfig.h"
 
+#if !defined(CMINUSMINUS)
+#include "rts/storage/HeapAlloc.h"
+#endif
+
 /* The actual block and megablock-size constants are defined in
  * rts/include/Constants.h, all constants here are derived from these.
  */
@@ -190,6 +194,7 @@ typedef struct bdescr_ {
 EXTERN_INLINE bdescr *Bdescr(StgPtr p);
 EXTERN_INLINE bdescr *Bdescr(StgPtr p)
 {
+  ASSERT(HEAP_ALLOCED_GC(p));
   return (bdescr *)
     ((((W_)p &  MBLOCK_MASK & ~BLOCK_MASK) >> (BLOCK_SHIFT-BDESCR_SHIFT))
      | ((W_)p & ~MBLOCK_MASK)