fix(lib): use -N syntax in `head` and `tail` to support Solaris (#6391)

lib/functions.zsh

 function zsh_stats() {
   fc -l 1 \
     | awk '{ CMD[$2]++; count++; } END { for (a in CMD) print CMD[a] " " CMD[a]*100/count "% " a }' \
-    | grep -v "./" | sort -nr | head -n20 | column -c3 -s " " -t | nl
+    | grep -v "./" | sort -nr | head -20 | column -c3 -s " " -t | nl
 }
 
 function uninstall_oh_my_zsh() {

lib/git.zsh

@@ -51,7 +51,7 @@ function parse_git_dirty() {
         FLAGS+="--ignore-submodules=${GIT_STATUS_IGNORE_SUBMODULES:-dirty}"
         ;;
     esac
-    STATUS=$(__git_prompt_git status ${FLAGS} 2> /dev/null | tail -n1)
+    STATUS=$(__git_prompt_git status ${FLAGS} 2> /dev/null | tail -1)
   fi
   if [[ -n $STATUS ]]; then
     echo "$ZSH_THEME_GIT_PROMPT_DIRTY"