Only build for arm64 on Kokoro

Change-Id: I80975241b061e58a0445abd42d3044678f75ff70
diff --git a/kokoro/build.sh b/kokoro/build.sh
index ee0632a..7bc9962 100644
--- a/kokoro/build.sh
+++ b/kokoro/build.sh
@@ -37,7 +37,7 @@
     ;;
 esac
 
-ARCHES="armhf arm64"
+ARCHES="arm64"
 
 for arch in ${ARCHES}
 do