Fix host-init-verifier regression

After the split up of prebuilt_internal.mk, the logic for running
host-init-verifier on init.rc files was misplaced.  This change moves
it back to the right location.

Test: see that a mistake in rootdir/init.rc causes the build to fail
Change-Id: I60e503cc48639f4f11c47e6636f140672fde61b4