[bug#39214] Updates to etc/guix-install.sh

Esteemed Maintainer,

Attached are two patches as a follow-up to https://debbugs.gnu.org/cgi/bugreport.cgi?bug=39049 that was just recently applied to the main source tree.

Patch 1 exports the INFOPATH and makes the up-to-date guix info manual available to the user via both /usr/bin/info and $GUIX_PROFILE/bin/info (previously `info guix` would either show the out-of-date info file installed during installation or throw a "No menu item 'guix' in node '(dir)Top" error if the $GUIX_PROFILE/bin/info was invoked, or if the info pages weren't installed during installation).

Patch 2 adds a defensive test against (highly unlikely) cases where /etc/profile.d might not exist, and creates it. The function does not quit on failure because it is possible that /etc/profile is still configured to read /etc/profile.d/*.sh files. Even if it is not, guix.sh will merely sit in /etc/profile.d and cause no changes to the user's environment.

These changes caused no regressions in my local machine.

I hope this helps more foreign distro users in their journey with Guix.

From:	Prafulla Giri
Subject:	[bug#39214] Updates to etc/guix-install.sh
Date:	Tue, 21 Jan 2020 12:56:34 +0545