Use -Werror in build/make

* Remove unused local variables.

Bug: 66996870
Test: build with WITH_TIDY=1
Change-Id: Iced5bb903902f49d7cd5cf5f572906a512c75e18
diff --git a/tools/fs_get_stats/Android.bp b/tools/fs_get_stats/Android.bp
index 6684319..67742b8 100644
--- a/tools/fs_get_stats/Android.bp
+++ b/tools/fs_get_stats/Android.bp
@@ -1,6 +1,7 @@
 cc_binary_host {
     name: "fs_get_stats",
     srcs: ["fs_get_stats.c"],
+    cflags: ["-Wall", "-Werror"],
     shared_libs: [
         "libcutils",
         "liblog",