Use -Werror in external/capstone

* Allow existing warnings.

Bug: 66996870
Test: build with WITH_TIDY=1
Change-Id: Idceea5c372f89707bb094cf73b4fb96671c903a0
diff --git a/Android.bp b/Android.bp
index 864a0ec..f580d14 100644
--- a/Android.bp
+++ b/Android.bp
@@ -38,7 +38,8 @@
     ],
     cflags: [
         "-Wall",
-        "-Wunused-parameter",
+        "-Werror",
+        "-Wno-error=unused-parameter",
         "-DCAPSTONE_USE_SYS_DYN_MEM",
     ],
     export_include_dirs: [".", "include"],