Without this fix, deploying `home-mcron-service-type' will strip user's PATH
variable from it's environment. This means that, programs such as `notmuch',
which use hooks which usually invoke `notmuch' from path, would need to be
updated with full paths; which makes it very inconvenient to use.
* gnu/services/mcron.scm (mcron-shepherd-services): respect user PATH variable.
Change-Id: I104aa0a818ad6c3266b2b8f73a9609bfb36e314d
Signed-off-by: Ludovic Courtès <ludo@gnu.org>