bind: add -Werror to gomobile bind CFLAGS

C compiler warnings are hidden in the gomobile build process. Expose
them through -Werror.

Change-Id: I2d87e5985f9ff874dc6feb836ba35c2bd848bfa6
Reviewed-on: https://go-review.googlesource.com/31517
Reviewed-by: David Crawshaw <crawshaw@golang.org>
diff --git a/bind/java/seq_android.go.support b/bind/java/seq_android.go.support
index d112159..f586e86 100644
--- a/bind/java/seq_android.go.support
+++ b/bind/java/seq_android.go.support
@@ -8,6 +8,7 @@
 // generated gomobile_bind package and compiled along with the
 // generated binding files.
 
+//#cgo CFLAGS: -Werror
 //#cgo LDFLAGS: -llog
 //#include <jni.h>
 //#include <stdint.h>
diff --git a/bind/objc/seq_darwin.go.support b/bind/objc/seq_darwin.go.support
index 3e4412e..38d6406 100644
--- a/bind/objc/seq_darwin.go.support
+++ b/bind/objc/seq_darwin.go.support
@@ -9,7 +9,7 @@
 // bindings.
 
 /*
-#cgo CFLAGS: -x objective-c -fobjc-arc
+#cgo CFLAGS: -x objective-c -fobjc-arc -Werror
 #cgo LDFLAGS: -framework Foundation
 
 #include <stdint.h>