Merge pull request #72812 from NixOS/bash-no-undef-vars

cc-wrapper, bintools-wrapper: Remove now unneeded `set {+,-}u`

pkgs/development/interpreters/lua-5/setup-hook.sh

@@ -20,7 +20,7 @@ addToLuaSearchPathWithCustomDelimiter() {
   if [[ ! -d "$topDir" ]]; then return; fi
 
   # export only if we haven't already got this dir in the search path
-  if [[ ${!varName} == *"$absPattern"* ]]; then return; fi
+  if [[ ${!varName-} == *"$absPattern"* ]]; then return; fi
 
   export "${varName}=${!varName:+${!varName};}${absPattern}"
 }