[ffmpeg] Temporarily disable -Wconversion warnings

While working on adding the `hwasan` variant, I unknowingly started
building ffmpeg since it's not yet in the list of variants that can use
a prebuilt binary. This temporarily disables -Wconversion to unblock
this work and some `fx format-code` changes.

Bug: 64191, 57112
Change-Id: Iad8c0da940291a568a058623a9f798147b95b368
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/ffmpeg/+/449862
Reviewed-by: Roland McGrath <mcgrathr@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index 3097816..a675da7 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -159,9 +159,7 @@
   cflags = []
   ldflags = []
   libs = []
-  deps = [
-    "//third_party/opus",
-  ]
+  deps = [ "//third_party/opus" ]
 
   configs += [
     ":ffmpeg_warnings",
@@ -223,9 +221,12 @@
     deps += [ ":ffmpeg_yasm" ]
   }
 
-  # TODO(46940): UBSan has found an instance of undefined behavior in this target.
+  # TODO(fxbug.dev/46940): UBSan has found an instance of undefined behavior in this target.
   # Disable UBSan for this target temporarily until it is migrated into CI/CQ.
   configs += [ "//build/config:temporarily_disable_ubsan_do_not_use" ]
+
+  # TODO(fxbug.dev/64191): Fix instances of -Wconversion errors found in ffmpeg.
+  configs += [ "//build/config:Wno-conversion" ]
 }
 
 group("ffmpeg_variants") {