Do not fail if there is no "$temp"/res.* file

Do not fail if there is no "$temp"/res.* file

find-debuginfo is multi-threaded and rpm runs
scripts usually with "-e" to abort on error.
If the debug-splitting tool fails, that job will abort.
But if you have X files that are problematic in the tree,
and you have X or less jobs, find-debuginfo will abort
as no single res.$number has been written.
But if you have more than X jobs, the build will succeed,
which makes the whole process random.
This commit remove this randomness.