Build with pthread support am: 8237422d3e

Original change: https://android-review.googlesource.com/c/platform/external/libevent/+/1552645

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I66a0c2f4dc8af8065e68ebb5dd306af6aa4a64e8
diff --git a/Android.bp b/Android.bp
index 3dd70f4..77a9868 100644
--- a/Android.bp
+++ b/Android.bp
@@ -51,6 +51,7 @@
         "event.c",
         "evmap.c",
         "evthread.c",
+        "evthread_pthread.c",
         "evutil.c",
         "evutil_rand.c",
         "evutil_time.c",