GitLab

resourcereadconfigfile.h is not installed into utils/

REVIEW: 126072

[-Wclazy-qgetenv]

This can properly cope with relative paths, something that the
previous code did not as QUrl::fromLocalFile would always
use the file scheme, and thus file:relative/path would be returned...

This fixes --msg and --attach with relative paths for me when
kmail was started ina different directory.

openComposer calls fromLocalFile on the string input,
so we better pass in a local file as well.