Make 32 bit builds via cmake possible on macos.

Working with ninja, make, and xcode generators using the
following args at cmake generation time:
-DAOM_TARGET_CPU=x86 -DCMAKE_OSX_ARCHITECTURES=i386 -DCONFIG_PIC=1

BUG=https://bugs.chromium.org/p/aomedia/issues/detail?id=76

Change-Id: I830db21f7458417cb8048818e5681a78698a6068
2 files changed