configure: give check_for() the ability to test several item types at once

Currently, check_for() can only test one of prog, inc or lib at once. This patch
removes this limitation.

Signed-off-by: "Benoît THÉBAUDEAU" <benoit.thebaudeau@advansee.com>

 reporter_name="Remy Bohmer"

 reporter_url="linux@bohmer.net"

 reporter_comment="Example for building a toolchain for m68000 bare metal targets"