Utilize variables for the build in more places

[apg]

• Update all the makefiles to reference $(MAKE) in case you invoked the build with gmake (as on OpenBSD)
• Prefer cc on OpenBSD, and update the mosmlc.tpl parameterize CC
• Support PREFIX=/path/ make world install
• Remove warnings from sizes.c test with %ld instead of %d.
• Ensure $cc is used instead of hardcoded gcc in autoconf

With this, I'm able to gmake world and install on the latest OpenBSD. I can test this, also on Linux, but I don't have access to other machine types at the moment to ensure I didn't break anything.

[apg]

I think I found the issue. Sorry for the force push. -Wnone... which I may have hallucinated ... as gcc errors, and I don't see it in the LLVM docs.