crossgcc: Fix colors with dash

crossgcc: Fix colors with dash

Ubuntu (and probably other distros) have dash as /bin/sh, which
doesn't display colors by itself. If /usr/bin/printf is found, it's
used instead of the internal printf to re-enable colors.

Change-Id: I3e6d413cd0c8a46ef91821d8c07e88166de58af4
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-on: http://review.coreboot.org/352
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>