Bionic includes are the same on all architectures, modulo
architecture-specific includes. Use a single function to populate the
list, passing in bionic's and the kernel's names for the architecture.
Also get rid of the ${LibcRoot} variable, it is not providing any value
and makes grepping harder.
Change-Id: I39e7907d312f52dd1378a3937ab1bcba12c4e97f