Tests: Fix new GCC 12 warnings

Author: https://github.com/BertalanD
Commit: 699bd9afc6
Pull-request: https://github.com/SerenityOS/serenity/pull/13954
Reviewed-by: https://github.com/ADKaster
Reviewed-by: https://github.com/EWouters
Reviewed-by: https://github.com/timschumi ✅

Tests/Kernel/crash.cpp

@@ -139,7 +139,10 @@ int main(int argc, char** argv)
                 return Crash::Failure::UnexpectedError;
 
             free(uninitialized_memory);
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wuse-after-free"
             [[maybe_unused]] volatile auto x = uninitialized_memory[4][0];
+#pragma GCC diagnostic pop
             return Crash::Failure::DidNotCrash;
         }).run(run_type);
     }
@@ -161,8 +164,11 @@ int main(int argc, char** argv)
             if (!uninitialized_memory)
                 return Crash::Failure::UnexpectedError;
 
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wuse-after-free"
             free(uninitialized_memory);
             uninitialized_memory[4][0] = 1;
+#pragma GCC diagnostic pop
             return Crash::Failure::DidNotCrash;
         }).run(run_type);
     }