Wrap InstallRequirement.ensure_build_location in TempDirectory
Wrap InstallRequirement.ensure_build_location in TempDirectory

Since we explicitly disable deletion this is a no-op, but we'll
parameterize the deletion soon.

pfmoore/pip,sbidoul/pip,pfmoore/pip,pradyunsg/pip,sbidoul/pip,pypa/pip,pypa/pip,pradyunsg/pip