PR34309: debuginfod: support relative source paths for reproducible builds

PR34309: debuginfod: support relative source paths for reproducible builds

Relaxed constraint checks in debuginfod-client and debuginfod-find to
allow relative source filenames (e.g. those starting with '.'  or
normal filenames), supporting binaries built with options like
-fdebug-prefix-map as one way to produce reproducible builds.  Note
that such paths will not generally be resolvable by debuginfod within
packages, nor if debuginfod's startup PWD is different from the build
tree.  This is a niche function only.

Added tests/testfile-debug-map{.c,.bz2} compiled with -fdebug-prefix-map
and tests/run-debuginfod-debug-map.sh to verify.

Signed-off-By: Frank Ch. Eigler <fche@redhat.com>
Reviewed-By: Aaron Merey <amerey@redhat.com>