runtime(zsh,sh): set and unset compiler in ftplugin

closes: #15699

Signed-off-by: Konfekt <Konfekt@users.noreply.github.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/ftplugin/sh.vim b/runtime/ftplugin/sh.vim
index c47aa52..d2faf1a 100644
--- a/runtime/ftplugin/sh.vim
+++ b/runtime/ftplugin/sh.vim
@@ -4,7 +4,7 @@
 " Previous Maintainer:	Dan Sharp
 " Contributor:		Enno Nagel <ennonagel+vim@gmail.com>
 "			Eisuke Kawashima
-" Last Change:		2024 May 06 by Vim Project (MANPAGER=)
+" Last Change:		2024 Sep 19 by Vim Project (compiler shellcheck)
 
 if exists("b:did_ftplugin")
   finish
@@ -54,6 +54,11 @@
   endif
   setlocal keywordprg=:ShKeywordPrg
   let b:undo_ftplugin ..= " | setl kp< | sil! delc -buffer ShKeywordPrg"
+
+  if !exists('current_compiler')
+    compiler shellcheck
+  endif
+  let b:undo_ftplugin .= ' | compiler make'
 endif
 
 let &cpo = s:save_cpo