Move memtag_stack out of libc_globals

We cannot use a WriteProtected because we are accessing it in a
multithreaded context.

Test: atest memtag_stack_dlopen_test w/ MTE
Test: atest bionic-unit-tests w/ MTE
Test: atest bionic-unit-tests on _fullmte
Bug: 328256432
Change-Id: I39faa75f97fd5b3fb755a46e88346c17c0e9a8e2
diff --git a/libc/bionic/malloc_common.cpp b/libc/bionic/malloc_common.cpp
index 3c4884b..9932e3e 100644
--- a/libc/bionic/malloc_common.cpp
+++ b/libc/bionic/malloc_common.cpp
@@ -353,7 +353,7 @@
       errno = EINVAL;
       return false;
     }
-    *reinterpret_cast<bool*>(arg) = atomic_load(&__libc_globals->memtag_stack);
+    *reinterpret_cast<bool*>(arg) = atomic_load(&__libc_memtag_stack);
     return true;
   }
   if (opcode == M_GET_DECAY_TIME_ENABLED) {