In r307676, several make rules were added for LLVM IR files, both in
text and binary format. Unfortunately these use different suffixes from
what upstream uses:
* Text IR has upstream suffix ".ll", while r307676 uses ".llo"
* Binary IR has upstream suffix ".bc", while r307676 uses ".bco"
Change these to what upstream uses instead.
Reviewed by: emaste
Differential Revision: https://reviews.freebsd.org/D8326