[Bug 57391] New: FSCTL_DISMOUNT_VOLUME does not work on drives with spaces in path

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=57391

Bug ID: 57391
           Summary: FSCTL_DISMOUNT_VOLUME does not work on drives with
                    spaces in path
           Product: Wine
           Version: 9.20
          Hardware: x86-64
                OS: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: ntdll
          Assignee: [e-mail]
          Reporter: [e-mail]
      Distribution: ---

After investigating, it looks like the FSCTL_DISMOUNT_VOLUME ioctl is
implemented by manually calling `umount` on the volume's mount path, but the
program is invoked using `system` instead of via other methods. This means
spaces in the volume path are not handled correctly and the volume is never
actually unmounted.

Reproduction:
* Insert a DVD/Blu-ray and mount it at a path including a space.
* Run `wine eject <drive letter>:

Results: Drive is not ejected
Expected: Drive is rejected

Attached are strace calls on two paths (one with a space, one without) showing
the issue.