Suppress -Wimplicit-fallthrough.

-Wimplicit-fallthrough will be enabled globally.

Test: build with global -Wimplicit-fallthrough.
Change-Id: I3793ff301b5ef79abf5bf092c159a659a6aea8d5
diff --git a/Android.bp b/Android.bp
index e81c5b4..8804072 100644
--- a/Android.bp
+++ b/Android.bp
@@ -29,6 +29,7 @@
         "-Wno-unused-parameter",
         "-Wno-maybe-uninitialized",
         "-Wno-missing-field-initializers",
+        "-Wno-implicit-fallthrough",
         "-Wwrite-strings",
         "-Werror",
         "-Dsprintf=sprintf",