apple-sdk_26-test: fix by using apple-sdk_26

This should now build in nixpkgs, with the same behavior as when using
the Xcode toolchain.

pkgs/by-name/ap/apple-sdk_26-test/package.nix

@@ -3,6 +3,7 @@
   stdenv,
   meson,
   ninja,
+  apple-sdk_26,
 }:
 
 stdenv.mkDerivation {
@@ -15,5 +16,9 @@ stdenv.mkDerivation {
     ninja
   ];
 
+  buildInputs = [
+    apple-sdk_26
+  ];
+
   meta.mainProgram = "apple-sdk_26-test";
 }