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

This reverts commit c567e447.

Reason for revert: Broke V8 Linux - arm64 - sim - MSAN (tree closed)

Original change's description:
> cppgc: Limit stack scan to clang-only
> 
> Quickfix to get non-clang bots green.
> 
> Bug: v8:10370
> Change-Id: I83591cd2bda94cd5aaffd023fe2b7068bdc7442f
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2131066
> Reviewed-by: Anton Bikineev <bikineev@chromium.org>
> Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#66928}

TBR=mlippautz@chromium.org,bikineev@chromium.org

Change-Id: I0e41e1caae696c6cb7dceeb48fa9a3ab277b5b66
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:10370
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2130759Reviewed-by: Zhi An Ng <zhin@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66929}

src/heap/cppgc/stack.h

@@ -8,11 +8,9 @@
 #include "src/base/macros.h"
 
 // TODO(chromium:1056170): Implement all platforms.
-#ifdef __clang__
-#if defined(V8_HOST_ARCH_X64)
+#if defined(V8_TARGET_ARCH_X64)
 #define CPPGC_SUPPORTS_CONSERVATIVE_STACK_SCAN 1
 #endif
-#endif
 
 namespace cppgc {
 namespace internal {