[Wconversion] Suppress warnings

Bug: 58162
Change-Id: Ie7491f5797c1fe21140803637674e5e3a43f90b2
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/mesa/+/431675
Reviewed-by: Petr Hosek <phosek@google.com>
diff --git a/src/BUILD.gn b/src/BUILD.gn
index 804d5cb..b28489a 100644
--- a/src/BUILD.gn
+++ b/src/BUILD.gn
@@ -110,6 +110,7 @@
     "-Wno-tautological-constant-out-of-range-compare",
     "-Wno-unknown-pragmas",
     "-Wno-int-in-bool-context",
+    "-Wno-conversion",
   ]
 }