setup.sh: fatal: Undefined variable

define hook arrays before assigning to them

pkgs/stdenv/generic/setup.sh

@@ -312,6 +312,10 @@ declare -a pkgTargetHookVars=(envTargetTargetHook)
 
 declare -a pkgHookVarVars=(pkgBuildHookVars pkgHostHookVars pkgTargetHookVars)
 
+# those variables are declared here, since where and if they are used varies
+# shellcheck disable=SC2034
+declare -a preFixupHooks fixupOutputHooks preConfigureHooks postFixupHooks postUnpackHooks unpackCmdHooks
+
 # Add env hooks for all sorts of deps with the specified host offset.
 addEnvHooks() {
     local depHostOffset="$1"