Check for both ISA and non-ISA specific files.

This helps in the multiarch+sngl case where the interpreter may not be
multiarch'd, for example /usr/bin/bash, but may also be applicable for
multiarch-only situations.
Merge branch 'joyent/feature/multiarch/2012Q4' into joyent/release/2012Q4_sngl

Conflicts:
	mk/check/check-interpreter.mk