LocationsManager: fix SYSROOT normalization to handle empty SYSROOT

This issue was exposed when building portage-2.3.34 with USE="epydoc"
enabled, since epydoc triggers instantiation of portage.settings.
The empty SYSROOT change for bug 654600 (in commit
1b5110557d1dd725f7c12bbed4b7ceaaec29f2a3) triggered incorrect
normalization behavior here.

Fixes: a41dacf7926c ("Export SYSROOT and ESYSROOT in ebuild env in EAPI 7")
1 file changed