file_contexts: remove symlink to binary file and use text version instead

Some older update binaries can't read the binary file_contexts, so include
the text version of the file to prevent errors. This removes the symlink
to the binary version of the file and uses the concatenated file_contexts
from the OUT build folder.

Change-Id: Ia57c9b47c95945721d3dfa1ec8e18c4bb199adff