Add support for in-place relocation

Virtualenv-clone could provide a command-line option to relocate a virtualenv's pathing (/bin shebangs and symlinks) without copying the virtualenv. This would be useful when preparing a virtualenv in a fake root directory for .rpm/.deb generation. A system package build process would create the virtualenv, install all dependencies into it, relocate the paths to exclude the fake root's prefix, and package up the fake root directory.

Creating a virtualenv in a chroot or container under a fake root directory works, but often isn't an option due to build pipelines' limited user accounts.

[hartwork]

Maybe rename to "Add support for in-place relocation". Just an idea.