openssl: fix Darwin cross infinite recursion

stdenv depends on openssl, and isGNU depends on stdenv.

Thanks-to: sternenseemann <0rpkxez4ksa01gb3typccl0i@systemli.org>
Fixes: https://github.com/NixOS/nixpkgs/issues/126829

pkgs/development/libraries/openssl/default.nix

@@ -54,7 +54,10 @@ let
 
     outputs = [ "bin" "dev" "out" "man" ] ++ optional withDocs "doc";
     setOutputFlags = false;
-    separateDebugInfo = !(stdenv.hostPlatform.useLLVM or false) && stdenv.cc.isGNU;
+    separateDebugInfo =
+      !stdenv.hostPlatform.isDarwin &&
+      !(stdenv.hostPlatform.useLLVM or false) &&
+      stdenv.cc.isGNU;
 
     nativeBuildInputs = [ perl ];
     buildInputs = lib.optional withCryptodev cryptodev