Reland "cppgc: Limit stack scan to clang-only"

Bug: v8:10370
Change-Id: Ia20388951ce420bdcd47d3c884ce762b87eefdf1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2130272Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Commit-Queue: Anton Bikineev <bikineev@chromium.org>
Auto-Submit: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66931}

src/heap/cppgc/stack.h

@@ -8,9 +8,13 @@
 #include "src/base/macros.h"
 
 // TODO(chromium:1056170): Implement all platforms.
+// TODO(chromium:1056170): Should use HOST arch instead of target arch. Fix
+// requires fixing e.g. simulator platforms.
+#ifdef __clang__
 #if defined(V8_TARGET_ARCH_X64)
 #define CPPGC_SUPPORTS_CONSERVATIVE_STACK_SCAN 1
 #endif
+#endif
 
 namespace cppgc {
 namespace internal {