Suppress implicit-fallthrough warnings.

Add FALLTHROUGH_INTENDED for clang compiler.

Bug: 112564944
Test: build with global -Wimplicit-fallthrough.
Change-Id: I40f8bbf94e207c9dd90921e9b762ba51abab5777
diff --git a/libutils/Android.bp b/libutils/Android.bp
index 1c1bdf7..600c91c 100644
--- a/libutils/Android.bp
+++ b/libutils/Android.bp
@@ -59,6 +59,7 @@
         "-Werror",
     ],
     header_libs: [
+        "libbase_headers",
         "libutils_headers",
     ],
     export_header_lib_headers: [