darwin: fix make prepare, force prebuilt host compiler

also fix relative TARGET_OUT_INTERMEDIATES path on aosp/master

Change-Id: Ie26850726898dcd101eac88d29691a06a94648c5
selinux: remove dependency on libsepol static lib

runcon applet is including flask.h for constants

the only one required is SECCLASS_PROCESS (2)

Change-Id: Ia57abc21b291e7cbf81fdd031baaa5ac4436cbc8