Separate building and enabling libevent.

webrtc/BUILD.gn

 # Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 # TODO(kjellander): Rebase this to webrtc/build/common.gypi changes after r6330.
 
@@ skipping 104 matching lines @@
 
     if (is_clang) {
       cflags += [
         "-Wimplicit-fallthrough",
         "-Wthread-safety",
         "-Winconsistent-missing-override",
       ]
     }
   }
 
+  if (rtc_enable_libevent) {
+    defines += [ "WEBRTC_BUILD_LIBEVENT" ]
+  }
+
   if (current_cpu == "arm64") {
     defines += [ "WEBRTC_ARCH_ARM64" ]
     defines += [ "WEBRTC_HAS_NEON" ]
   }
 
   if (current_cpu == "arm") {
     defines += [ "WEBRTC_ARCH_ARM" ]
     if (arm_version >= 7) {
       defines += [ "WEBRTC_ARCH_ARM_V7" ]
       if (arm_use_neon) {
@@ skipping 173 matching lines @@
 if (use_libfuzzer || use_drfuzz) {
   # This target is only here for gn to discover fuzzer build targets under
   # webrtc/test/fuzzers/.
   group("webrtc_fuzzers_dummy") {
     testonly = true
     deps = [
       "test/fuzzers:webrtc_fuzzer_main",
     ]
   }
 }