Allow c2y-extensions in Tint w/ CMake

Applies https://dawn-review.googlesource.com/c/dawn/+/275695 when
building Tint with CMake.

Bug: 452840620
Change-Id: I49ded1772527aa1c2d6b64bbcc7e96c4758dd323
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/276095
Commit-Queue: Ryan Harrison <rharrison@chromium.org>
Auto-Submit: Brian Sheedy <bsheedy@google.com>
Reviewed-by: Ryan Harrison <rharrison@chromium.org>

src/tint/CMakeLists.txt

diff --git a/src/tint/CMakeLists.txt b/src/tint/CMakeLists.txt
index 13ab189..84947a1 100644
--- a/src/tint/CMakeLists.txt
+++ b/src/tint/CMakeLists.txt
@@ -115,6 +115,7 @@
     -Wunsafe-buffer-usage
     -Wno-unsafe-buffer-usage-in-libc-call
     -Wno-covered-switch-default
+    -Wno-c2y-extensions
   )
 
   if(COMPILER_IS_GNU)