Protect APM in webkit builds.

Update libwertc AudioRtpSender::SetAudioSend with WEBRTC_WEBKIT_BUILD

This only introduces the WEBRTC_WEBKIT BUILD, inspired by WEBRTC_CHROMIUM_BUILD
macro. It is only defined by Webkit libwebrtc build system.
https://trac.webkit.org/changeset/210977

BUG=webrtc:7039

Review-Url: https://codereview.webrtc.org/2651273003
Cr-Original-Commit-Position: refs/heads/master@{#16432}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: b11fb25c1230b2ef1085b9c0aa0642d6494afa88
1 file changed