'nix-daemon' now creates subdirectories for users when they first
connect.
Fixes#509 (CVE-2019-17365).
Should also fix#3127.
(cherry picked from commit 5a303093dcae1e5ce9212616ef18f2ca51020b0d)
This removes part of the PATH that were being added automatically in multi-user installs:
- $HOME/.nix-profile/lib/kde4/libexec - shouldn't be needed anymore, we are now using kde5
- @localstatedir@/nix/profiles/default/lib/kde4/libexec - same as above
- @localstatedir@/nix/profiles/default - shouldn't ever contain binaries
If the profile is sourced inside a script with `set -u`, the check for
__ETC_PROFILE_NIX_SOURCED and NIX_SSL_CERT_FILE would raise an error.
A simple guard around this check allows the script to operate under
standard environments (where it is fairly reasonable to assume USER
and HOME are set.)