export_image.c: allow duplicate image names in source WIM
Reported at https://wimlib.net/forums/viewtopic.php?f=1&t=568. DISM can
create WIM files containing images with duplicate names, whereas wimlib
enforces unique image names in certain cases such as adding images,
exporting images, and changing image names. This behavior generally
seems fine, but the "export" check is too strict: an export of "all"
images will fail if the source WIM contains duplicate names.
Fix this by making wimlib_export_image() allow duplicate image names in
the source WIM, provided that they don't collide with image names that
already exist in the destination WIM.
git://wimlib.net / wimlib / commit