crossgcc: Support OSX 10.9 built-in tar utility program.

Unlike OSX 10.8, OSX 10.9 doesn't provide GNU tar program, and built-in
tar program is bsdtar 2.8.3. bsdtar can build crossgcc toolchain.
Modify buildgcc to support tar in OSX 10.9 (uname = Darwin).

Change-Id: I093898f8f99e29918387f9b275a30af461a7e1be
Signed-off-by: Andrew Wu <arw@dmp.com.tw>
Reviewed-on: http://review.coreboot.org/5598
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>
1 file changed