add offload target to testname for pass/fail message

add offload target to testname for pass/fail message

Offload tests that scan dump files may run multiple times, once per
offload target, but the test result messages do not mention the
offload target, so we may seem to have repeated results.  Fixed by
modifying the test name so that it contains the offload target name.

Co-Authored-By: Thomas Schwinge <thomas@codesourcery.com>
for  gcc/testsuite/ChangeLog

	* lib/scanoffload.exp (scoff-testname, scoff-adjust): New.
	(scoff): Call them.