gn2bp: Update define to cflag conversion

Test: m with Android.bp.swp
Change-Id: I7245120dcb414d7e45c722fa6393bf13cad6fb6d
diff --git a/tools/gn2bp/update_results.sh b/tools/gn2bp/update_results.sh
index e8583ba..31f6605 100755
--- a/tools/gn2bp/update_results.sh
+++ b/tools/gn2bp/update_results.sh
@@ -13,6 +13,7 @@
 
 TARGETS=(
   "//third_party/zlib:zlib"
+  "//third_party/libevent:libevent"
 )
 
 BASEDIR=$(dirname "$0")