Let genrule be mutatable by the apex mutator

genrule modules were not mutated by the apex mutator. As a result, a
module that is mutated for an apex have depended on the genrule modules
host_bionic_linker_{asm|flags} that are not mutated for the APEX.

This in turn caused an inconsistency problem because the
host_bionic_linker_* genrules use the dynamic linker that isn't mutated
for APEX as an input, while the outputs of the genrules are used by
modules mutated for APEX. The inconsistency caused b/135008828.

Fixing this issue by correctly let genrule to be mutated by the apex
mutator.

Bug: 135008828
Test: checkout master-art-host
ALLOW_MISSING_DEPENDENCIES=true DIST_DIR=out/dist
./art/tools/dist_linux_bionic.sh -j50 showcommands
com.android.runtime.host
is passing

Change-Id: I92d90400c61d3951f6202d932832d0cb63c95a7d