Disable -Wformat-insufficient-args for external code.

Bug: 191699019
Test: presubmit
Change-Id: I8af5ccdca4078468d6de2f6212045875d7c6541b
diff --git a/cc/config/global.go b/cc/config/global.go
index d557c0b..1aec190 100644
--- a/cc/config/global.go
+++ b/cc/config/global.go
@@ -293,6 +293,9 @@
 
 		// http://b/239661264
 		"-Wno-deprecated-non-prototype",
+
+		// http://b/191699019
+		"-Wno-format-insufficient-args",
 	}
 
 	llvmNextExtraCommonGlobalCflags = []string{