C++17 compatibility: `register` is no longer a keyword.

Bug: http://b/111067277
Test: builds
Change-Id: Iec895aa7b3e405b0427d14541d9c1cd9920841d2
diff --git a/Android.bp b/Android.bp
index 5b6120d..d75aa7c 100644
--- a/Android.bp
+++ b/Android.bp
@@ -29,6 +29,7 @@
         "-Wno-error=macro-redefined",
         "-Wno-int-conversion",
         "-Wno-missing-field-initializers",
+        "-Wno-register",
         "-Wno-shift-count-overflow",
         "-Wno-sign-compare",
         "-Wno-tautological-compare",