libdwfl: Try opening files all installed compression libraries.

rhbz #909481. When a compression library wasn't installed libdwfl would
not try the next compression library for opening a file. Retry with the
next available compression library if a previous one isn't installed. Also
disable tests that depend on a particular compression library
(run-readelf-s.sh and run-dwflsyms.sh) if that library isn't installed.

Signed-off-by: Mark Wielaard <mjw@redhat.com>
4 files changed