libbinder: export fewer symbols for vendor builds

See https://r.android.com/3087749 for details.

This commit brings the vendor build to parity with the other builds. It
may cause some initial issues for vendors, but that should be more than
compensated by the ongoing issues it will fix for them. For example,
when backporting security fixes, we'd often see ABI breakages because
the set of internal symbols might change (before this commit we'd be
exporting all internal symbols). That should never happen after this
change.

Bug: 338458975
Bug: 349657329
Test: m
Change-Id: I5f77a8d1e16d38c5e83f9b8842368a967b4ee229

Author: fkm3

libs/binder/Android.bp

@@ -276,15 +276,6 @@ cc_defaults {
         "-fvisibility=hidden",
         "-DBUILDING_LIBBINDER",
     ],
-
-    target: {
-        vendor: {
-            // Trimming the exported symbols reveals a bug in vendor code, so
-            // disable it for the vendor variant for now. http://b/349657329
-            // TODO: Fix the issue and remove this override.
-            cflags: ["-fvisibility=default"],
-        },
-    },
 }
 
 cc_defaults {