Ha! That was it! It builds now and runs.
Just had to make this change in the os_osx.mk file
OPT_CPU = x64
Thanks Joel.
(by the way)
in gdriver.h, line 90, there are two const declarations in the same line, which the gcc compiler on the mac is not happy with.
just generates a warning).
Same issue on gdisp_driver.h, line 735.