Utilities/Release: Fix 'git archive' invocation

Tell it not to consider the current work tree location.
Utilities/Release: Use in-PATH sphinx-build on dash2win64
Merge topic 'doc-release-tarball' into next

9b7cd099 Utilities/Release: Use in-PATH sphinx-build on dash2win64
460b0f5d Utilities/Release: Fix 'git archive' invocation