drm-shim: drop gnu99 override

If we override with gnu99 here, we effectively down-grade from C11,
meaning we can no longer assume static_assert support.

Fixes: 45fb815a75 ("util: implement STATIC_ASSERT using c++11 / c11 primitives")

Signed-off-by: Yonggang Luo <luoyonggang@gmail.com>
Suggested-by: Chia-I Wu <olvaffe@gmail.com>
Reviewed-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Reviewed-by: Eric Engestrom <eric@igalia.com>
Reviewed-by: Chia-I Wu <olvaffe@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/18611>
(cherry picked from commit a9f3e011e5)

.pick_status.json

@@ -5692,7 +5692,7 @@
         "description": "drm-shim: drop gnu99 override",
         "nominated": true,
         "nomination_type": 1,
-        "resolution": 0,
+        "resolution": 1,
         "main_sha": null,
         "because_sha": "45fb815a75669b32f6317ba6d53ec9465a4b0ae0"
     },

src/drm-shim/drm_shim.c

@@ -52,7 +52,7 @@
 #include "util/u_debug.h"
 #include "drm_shim.h"
 
-#define REAL_FUNCTION_POINTER(x) typeof(x) *real_##x
+#define REAL_FUNCTION_POINTER(x) __typeof__(x) *real_##x
 
 static mtx_t shim_lock = _MTX_INITIALIZER_NP;
 struct set *opendir_set;

src/drm-shim/meson.build

@@ -28,7 +28,6 @@ drm_shim = static_library(
   include_directories: [inc_include, inc_src, inc_mapi, inc_mesa, inc_gallium, inc_gallium_aux],
   dependencies: [dep_libdrm, idep_mesautil, dep_dl],
   gnu_symbol_visibility : 'hidden',
-  override_options : ['c_std=gnu99'],
 )
 dep_drm_shim = declare_dependency(
   link_with: drm_shim,