Propagate target OS from configure to Makefile

Propagate target OS from configure to Makefile (CONFIG_TARGET_OS) to avoid
duplicating the check in Makefile.  Also allow CROSS_COMPILE for the toolchain
prefix, which is common (e.g. Linux).

Signed-off-by: Aaron Carroll <aaronc@cse.unsw.edu.au>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2 files changed