Do not use libevent when targeting wasm.

Bug: None
Change-Id: Ibfab54e2d1504b5add54ecaff6cf0935967cbb88
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/142809
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Oleh Prypin <oprypin@webrtc.org>
Reviewed-by: Steve Anton <steveanton@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28329}
diff --git a/webrtc.gni b/webrtc.gni
index 77ed45f..d7cc238 100644
--- a/webrtc.gni
+++ b/webrtc.gni
@@ -221,7 +221,8 @@
   rtc_build_usrsctp = !build_with_mozilla
 
   # Enable libevent task queues on platforms that support it.
-  if (is_win || is_mac || is_ios || is_nacl || is_fuchsia) {
+  if (is_win || is_mac || is_ios || is_nacl || is_fuchsia ||
+      target_cpu == "wasm") {
     rtc_enable_libevent = false
     rtc_build_libevent = false
   } else {