Add the metalava_enabled property

The new property is added for supporting metalava. But some sdk library
cannot use metalava. So "metalava_enabled: false" is added to these
modules.

Test: make -j
Test: checkapi
Change-Id: I334402a69e25f9d32cebe07c1f51a133cd8e966e
diff --git a/Android.bp b/Android.bp
index 0b71d63..d3fd54b 100644
--- a/Android.bp
+++ b/Android.bp
@@ -75,4 +75,5 @@
     errorprone: {
         javacflags: ["-Xep:MissingOverride:OFF"],  // b/73499927
     },
+    metalava_enabled: false,
 }