virtualbox: Fix invalid share names in Windows guests

[legal90]

That PR fixes invalid share names in Windows guests, where backward slash character is
used as a path separator.

Details:
Currently, if we define the synced folder this way (for Windows guest):

config.vm.synced_folder "../", 'C:\Users\vagrant\my_share'

then the share id will be this string: 'C:\Users\vagrant\my_share'
In the guest it will be exposed as \\VBOXSRV\C:\Users\vagrant\my_share, which is an invalid path, so the share will not be available.

This Pull-Request adds \ to the regex, so this char will be replaced with _.
The result share id will be 'C:_Users_vagrant_my_share' and it will be available at \\VBOXSRV\C:_Users_vagrant_my_share without any issues.

The similar PR has been sent to Parallels provider: Parallels/vagrant-parallels#296

[chrisroberts]

👍 Thanks!

[legal90]

@chrisroberts Thank you for merging this PR! 🎉
However, the changelog note is not quite right:

hosts/windows: Fix invalid share names on Windows guests from Windows hosts [GH-8433]

This issue & fix are not specific to Windows hosts only. I guess it is relevant to any host OS. In particular, I've reproduced in on macOS.

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you have found a problem that seems similar to this, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.