ld: ld-lib.exp: log failed dump.out contents for debugging

ld: ld-lib.exp: log failed dump.out contents for debugging

If we're using dump_prog in a test which fails, log the dump.out contents
to ld.log to aid debugging.

This avoids needing to ask reporters to manually run e.g. `objdump` commands
when making bug reports.

PR30722
	* ld/testsuite/lib/ld-lib.exp: Log failed dump.out contents to aid
	debugging.

Approved-by: Nick Clifton <nickc@redhat.com>
Signed-off-by: Sam James <sam@gentoo.org>
(cherry picked from commit 646657284f6b62a71a6869826e951b3def4d73a6)