Fix iterating over $NIX_PROFILES in Zsh

NIX_PROFILES is space separated list of directories, and passing it into
for as is is considered to be 1-element list with the whole string. With
shwordsplit option Zsh emulates other shells in this regard ans
implicitely splits unquoted strings into words.

Fixes #4167.

scripts/nix-profile-daemon.sh.in

@@ -17,11 +17,21 @@ elif [ -e /etc/pki/tls/certs/ca-bundle.crt ]; then # Fedora, CentOS
     export NIX_SSL_CERT_FILE=/etc/pki/tls/certs/ca-bundle.crt
 else
   # Fall back to what is in the nix profiles, favouring whatever is defined last.
+  check_nix_profiles() {
+    if [ "$ZSH_VERSION" ]; then
+      # Zsh by default doesn't split words in unquoted parameter expansion.
+      # Set local_options for these options to be reverted at the end of the function
+      # and shwordsplit to force splitting words in $NIX_PROFILES below.
+      setopt local_options shwordsplit
+    fi
     for i in $NIX_PROFILES; do
       if [ -e $i/etc/ssl/certs/ca-bundle.crt ]; then
         export NIX_SSL_CERT_FILE=$i/etc/ssl/certs/ca-bundle.crt
       fi
     done
+  }
+  check_nix_profiles
+  unset -f check_nix_profiles
 fi
 
 export PATH="$HOME/.nix-profile/bin:@localstatedir@/nix/profiles/default/bin:$PATH"