Use -Werror in external/selinux

* Use -Wno-error= to keep existing warnings to fix later.

Bug: 66996870
Test: build with WITH_TIDY=1
Change-Id: Id7d641c73f396c37c1fb8c5228919c722e2bedd3
diff --git a/checkpolicy/Android.bp b/checkpolicy/Android.bp
index 1ca0e07..bfd91b7 100644
--- a/checkpolicy/Android.bp
+++ b/checkpolicy/Android.bp
@@ -21,6 +21,7 @@
 
 cc_binary_host {
     name: "dispol",
+    cflags: common_CFLAGS,
     srcs: ["test/dispol.c"],
     static_libs: ["libsepol"],
 }