ld: Create test object files based on source file name

ld: Create test object files based on source file name

When creating object files during testing, base the name of the object
file on the name of the source file, rather than using dump0.o,
dump1.o, etc.  There's a few places where we have multiple source
files with the same name but in different directories, in these cases,
even after this change, we still add a numerical suffix to make the
object file names unique.  So if we have 'foo/src.s' and 'bar/src.s',
we will create object files 'src.o' and 'src1.o'.

Update the few tests that hard code the object file name into the
expected test results.

ld/ChangeLog:

	* testsuite/lib/ld-lib.exp (run_dump_test): Use object file names
	based on the original source file name.
	* testsuite/ld-discard/extern.d: Update object file names.
	* testsuite/ld-discard/start.d: Likewise.
	* testsuite/ld-discard/static.d: Likewise.
	* testsuite/ld-elf/orphan-8.map: Likewise.