gnu: runc, skopeo, docker-cli, umoci: Don't 'chdir' in build phases.

This fixes breaks the 'install-license-files' phase added in
6b793fa6 and is generally not good
practice.

Reported by divoplade on #guix.

* gnu/packages/virtualization.scm (runc)[arguments]: Use
'with-directory-excursion' instead of 'chdir' in build phases.
(skopeo)[arguments]: Likewise.
(umoci)[arguments]: Likewise.
* gnu/packages/docker.scm (docker-cli)[arguments]: In 'install' phase,
remove call to 'chdir' and adjust 'install-file' argument accordingly.