Restrict header visibility again

STG no longer depends on libabigail (at all). Default visibility is
reverted back to private and the target libabigail_src_headers is
removed.

This change mostly reverts 42c7a4e0f3de but leaves the include
directory as part of the libabigail's exported headers.

Change-Id: Ic89dc7049c15ce98729cfcdcae02ae9f6626f0c5
Signed-off-by: Giuliano Procida <gprocida@google.com>
1 file changed