binutils: Add do_check task for executing binutils test suite

binutils: Add do_check task for executing binutils test suite

Create the do_check task to the binutils-cross include. This task can be
used to execute the binutils test suite for the cross target binutils.
By default this executes all the check targets of the binutils Makefile,
this can however be changed by setting MAKE_CHECK_TARGETS to the desired
test suite target (e.g. check-gas).

The binutils test suites do not require any target execution, as such
the check target can be run without QEMU or a target device. However
since the binutils tests do rely on a C compiler there is dependence on
both gcc and libc in order to run the tests.

Signed-off-by: Nathan Rossi <nathan@nathanrossi.com>
Signed-off-by: Armin Kuster <akuster808@gmail.com>