When passing `-o` flags to other options, the typical `-o foo` spelling leaves a leading whitespace when replacing elsewhere. This ends up creating flags spelled as `-some-option-with-arg= foo.ext` which doesn't parse properly. When attempting to make a spec function to just remove the leading whitespace, the argument splitting ends up masking the whitespace. However, the intended extension *also* ends up being its own argument. To perform the desired behavior, the arguments need to be concatenated together. gcc/: * gcc.cc (join_spec_func): Add a spec function to join all arguments. Signed-off-by: Ben Boeckel <ben.boeckel@kitware.com> Co-authored-by: Jason Merrill <jason@redhat.com>