BRIG FE testsuite: Fix all dump-scans

BRIG FE testsuite: Fix all dump-scans

since Alexandre's revamp of dump files handling in
r11-627-g1dedc12d186, BRIG FE has been receiving slightly different
-dumpbase (e.g. smoke_test.brig instead of smoke_test.hsail.brig when
compiling file smoke_test.hsail.brig) and the testsuite then could not
find the generated dump files it wanted to scan.  I have not really
looked into why that changed, the easiest fix seems to me to remove
the hsail part already when generating the binary brig file from the
textual HSAIL representation.

gcc/testsuite/ChangeLog:

2020-06-09  Martin Jambor  <mjambor@suse.cz>

	* lib/brig.exp (brig_target_compile): Strip hsail extension when
	gnerating the name of the binary brig file.