[build] Suppress implicit conversion errors

This change suppress implicit conversion errors in ffmpeg to unblock
the build.

Bug: 62466
Change-Id: Ica67b30099ce35d98a9a8fa0fc4a1092d797464c
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/ffmpeg/+/441538
Reviewed-by: Petr Hosek <phosek@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index a7d14048..3097816 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -2,8 +2,8 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-import("ffmpeg_options.gni")
 import("ffmpeg_generated.gni")
+import("ffmpeg_options.gni")
 
 # Path to configuration files.
 ffmpeg_config_root = "fuchsia/config/$ffmpeg_profile/$current_cpu"
@@ -115,6 +115,7 @@
     # to confirm if this indentation is expected.
     "-Wno-misleading-indentation",
   ]
+  configs = [ "//build/config:Wno-conversion" ]
 }
 
 config("ffmpeg_warnings") {