gstreamer: Fix wrapper quoting

The bug was that the inner double quotes in "\$("…")" are not actually
inner like they would be in "$("…")".  We could write "\$(\"…\")", but
using single quotes on the outside makes everything simpler.

Fixes #63751.

Signed-off-by: Anders Kaseorg <andersk@mit.edu>

pkgs/development/libraries/gstreamer/core/default.nix

@@ -99,7 +99,7 @@ stdenv.mkDerivation rec {
   postInstall = ''
     for prog in "$dev/bin/"*; do
         # We can't use --suffix here due to quoting so we craft the export command by hand
-        wrapProgram "$prog" --run "export GST_PLUGIN_SYSTEM_PATH=\$GST_PLUGIN_SYSTEM_PATH"$\{GST_PLUGIN_SYSTEM_PATH:+:\}"\$(unset _tmp; for profile in \$NIX_PROFILES; do _tmp="\$profile/lib/gstreamer-1.0''$\{_tmp:+:\}\$_tmp"; done; printf "\$_tmp")"
+        wrapProgram "$prog" --run 'export GST_PLUGIN_SYSTEM_PATH=$GST_PLUGIN_SYSTEM_PATH''${GST_PLUGIN_SYSTEM_PATH:+:}$(unset _tmp; for profile in $NIX_PROFILES; do _tmp="$profile/lib/gstreamer-1.0''${_tmp:+:}$_tmp"; done; printf '%s' "$_tmp")'
     done
   '';