Disable -Wextra-semi.

WebRTC needs to compile with -Wextra-semi but since this code is not
WebRTC code, this CL suppresses the warning.

Bug: webrtc:10355
Change-Id: Iebd17b1ef06210f312eaaf1df64ba5897b707d9c
Reviewed-on: https://webrtc-review.googlesource.com/c/124700
Reviewed-by: Oleh Prypin <oprypin@webrtc.org>

BUILD.gn

diff --git a/BUILD.gn b/BUILD.gn
index cf4a7a5..b1442cd 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -32,6 +32,7 @@
         # Disable warnings failing when compiling with Clang on Windows.
         # https://bugs.chromium.org/p/webrtc/issues/detail?id=5366
         "-Wno-comment",
+        "-Wno-extra-semi",
         "-Wno-delete-non-virtual-dtor",
         "-Wno-ignored-attributes",
         "-Wno-logical-op-parentheses",