core: combo: mac: allow building on Mavericks and Yosemite

Change-Id: Icd60190cc36f2f029c8a099e4d00d4112faa1eb0
core: combo: darwin: fix toolchain header inclusion on OS X > 10.8

Mavericks and Yosemite do not provide stdarg.h etc. either.

Change-Id: I750de04373ab7dca8f143fa8d9dcbd4e08dfdbf8
core: combo: darwin: do not run ranlib for OS X > 10.8 either

Change-Id: Icd4ca24f4e8e7016f9b59b05e9d68de0a86710d4