wrapGAppsHook: simplify taking env vars

using indirect variable access must be better than eval

pkgs/build-support/setup-hooks/wrap-gapps-hook.sh

@@ -41,8 +41,7 @@ wrapGAppsHook() {
   fi
 
   for v in $wrapPrefixVariables GST_PLUGIN_SYSTEM_PATH_1_0 GI_TYPELIB_PATH GRL_PLUGIN_PATH; do
-    eval local dummy="\$$v"
-    gappsWrapperArgs+=(--prefix $v : "$dummy")
+    gappsWrapperArgs+=(--prefix $v : "${!v}")
   done
 
   if [[ -z "$dontWrapGApps" ]]; then