Add m4 to the prebuilt build-tools
am: 9867042b2c

Change-Id: I88aeeadb97f5ef84da726b8799225a1b210cc078
diff --git a/build-prebuilts.sh b/build-prebuilts.sh
index 1758508..e6f400f 100755
--- a/build-prebuilts.sh
+++ b/build-prebuilts.sh
@@ -46,6 +46,7 @@
         ckati
         ckati_stamp_dump
         flex
+        m4
         make
         makeparallel
         ninja