Since !6239 (merged) the file(RPATH_...) operations fail on
files that are not ELF or XCOFF format. Previously the RPATH operations
tolerated files of unknown format if the goal was to produce a file with
an empty RPATH. Restore this tolerance in order to support setting an
empty RPATH on GNU ld scripts.
Fixes: #22963 (closed)
Backport: release