Use -Werror in development/vndk

Bug: 66996870
Test: build with WITH_TIDY=1
Change-Id: I3ec7453bf144671840b97a6e2e5549b4c7e3bcc1
diff --git a/vndk/tools/header-checker/Android.bp b/vndk/tools/header-checker/Android.bp
index 3f29d06..61a797c 100644
--- a/vndk/tools/header-checker/Android.bp
+++ b/vndk/tools/header-checker/Android.bp
@@ -118,6 +118,8 @@
     },
 
     cflags: [
+        "-Wall",
+        "-Werror",
         "-Wcast-qual",
         "-Wno-long-long",
         "-Wno-unused-parameter",