install.sh: improve POSIX compatibility

POSIX `find` do not support `-lname`:
https://pubs.opengroup.org/onlinepubs/9799919799/utilities/find.html

Author: chirsz-ever

uninstall.sh

@@ -385,7 +385,9 @@ do
 done
 if [[ "${#paths[@]}" -gt 0 ]]
 then
-  args=("${paths[@]}" -type l -lname '*/Cellar/*')
+  # We want expand in subcommand, not here
+  # shellcheck disable=SC2016
+  args=("${paths[@]}" -type l -exec /bin/sh -c 'case $(ls -l "{}") in *-\>\ */Cellar/*)exit;esac;exit 1')
   if [[ -n "${opt_dry_run}" ]]
   then
     args+=(-print)