Zsh: Change Gentoo repo directory aliases a bit

- Check for /etc/gentoo-release instead of calling lsb_release
- Make allrepos command nicer

.config/zsh/zaliases

@@ -85,8 +85,7 @@ alias machklein='mksmol'
 alias diff='diff --color=auto'
 
 # OS specific settings.
-case $(lsb_release -i -s 2> /dev/null) in
-    Gentoo)
+if [[ -f /etc/gentoo-release ]]; then
     # Directory aliases for some Gentoo paths
     for dir in /etc/portage/package.*; do
         hash -d -- -${dir##*/}=${dir}
@@ -118,9 +117,8 @@ case $(lsb_release -i -s 2> /dev/null) in
     }
     async_start_worker diralias_repo
     async_register_callback diralias_repo _my_diralias_repo_done
-        async_job diralias_repo "print -n "allrepos=" && portageq get_repos /"
-        ;;
-esac
+    async_job diralias_repo 'print -n "allrepos=$(portageq get_repos /)"'
+fi
 
 command -v apt-cache > /dev/null && alias qs="apt-cache search --names-only"