nixguix: Make nar ignore .hg and .svn folders as well
This aligns further with the guix hash command behavior.
$ guix hash -S nar -f base32 -H sha256 -x /var/tmp/panda apq7sedacxf2lqaebllbngtszci63v7cbwxmo4276k26nv4ocseq $ python -m nar -f base32 -H sha256 /var/tmp/panda apq7sedacxf2lqaebllbngtszci63v7cbwxmo4276k26nv4ocseq==== guix hash -S nar -f base32 -H sha256 -x /var/tmp/hgview lepywr37sfg4uqmetcww2q2hxjicgags3xt5fjbvjoepiqcluj5q $ python -m nar -f base32 -H sha256 /var/tmp/hgview lepywr37sfg4uqmetcww2q2hxjicgags3xt5fjbvjoepiqcluj5q====
Related to T4538#93319