fix #451: command -v is more portable than which because it is a built-in shell feature, and which is an external utility that is not necessarily installed

Author: yihui

tools/install-bin-unix.sh

@@ -7,7 +7,7 @@ perl -mFile::Find /dev/null ||
 
 cd ${TMPDIR:-/tmp}
 
-[ -z $(which tlmgr) ] || TL_INSTALLED_PKGS=$(tlmgr info --list --only-installed --data name | tr '\n' ' ')
+[ -z $(command -v tlmgr) ] || TL_INSTALLED_PKGS=$(tlmgr info --list --only-installed --data name | tr '\n' ' ')
 [ -z "$TL_INSTALLED_PKGS" ] ||
   echo "If you want to reinstall currently installed packages, use this command after the TinyTeX installation is done: