Remove leading whitespace in gnu-debugaltlink-name.sh output

Remove leading whitespace in gnu-debugaltlink-name.sh output

Currently, gnu-debugaltlink-name.sh prints leading whitespace:
...
$ echo \""$(./testsuite/scripts/gnu-debugaltlink-name.sh 1)"\"
"  3"
...

Fix this by using sed to extract the name from the readelf output.

With that fixed, we add quotes to gnu-debugaltlink-name.sh calls to prevent
"unary operator expected" errors.

2019-03-13  Tom de Vries  <tdevries@suse.de>

	* testsuite/scripts/gnu-debugaltlink-name.sh: Remove leading whitespace.
	* testsuite/dwz.tests/eu-strip-unstrip-multifile.sh: Guard
	gnu-debugaltlink-name.sh call with quotes.
	* testsuite/dwz.tests/multifile-name.sh: Same.
	* testsuite/dwz.tests/multifile-relative.sh: Same.
	* testsuite/dwz.tests/multifile.sh: Same.