Bug 2067405 - mark hal's sInitialized as maybe_unused. r=gsvelto

Every read of sInitialized happens inside a MOZ_ASSERT, so opt builds only ever write to it. clang 23
flags that under -Wunused-but-set-global, which -Wall now enables transitively via
-Wunused-but-set-variable, busting the plain clang-trunk build.

Differential Revision: https://phabricator.services.mozilla.com/D322068

hal/Hal.cpp

@@ -48,7 +48,7 @@ using namespace mozilla::dom;
 
 namespace mozilla::hal {
 
-static bool sInitialized = false;
+[[maybe_unused]] static bool sInitialized = false;
 
 mozilla::LogModule* GetHalLog() {
   static mozilla::LazyLogModule sHalLog("hal");