bug#20255: 'search-paths' should respect both user and system profile.

[宋文武 via Bug reports for GNU Guix]

Hello, commit 40310efde9b4a4f2cf98081d6cd10f843685ebb6 fix this by merge
search-paths from multiple profiles by `guix package --search-paths`, in
~/.bashrc and ~/.zprofile (skeletons, so existed systems need manual
update).  


Close now!