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>