python3Packages.pythran: use LLVM openmp when using clang

This fixes pythran (and, therefore, also scipy, etc.) under Darwin
builds, which use LLVM by default.

pkgs/development/python-modules/pythran/default.nix

@@ -2,6 +2,7 @@
 , python
 , buildPythonPackage
 , fetchFromGitHub
+, openmp
 , pytest-runner
 , ply
 , networkx
@@ -34,7 +35,7 @@ in buildPythonPackage rec {
     # Hardcode path to mp library
     (substituteAll {
       src = ./0001-hardcode-path-to-libgomp.patch;
-      gomp = "${stdenv.cc.cc.lib}/lib/libgomp${stdenv.hostPlatform.extensions.sharedLibrary}";
+      gomp = "${if stdenv.cc.isClang then openmp else stdenv.cc.cc.lib}/lib/libgomp${stdenv.hostPlatform.extensions.sharedLibrary}";
     })
   ];
 

pkgs/top-level/python-packages.nix

@@ -7341,7 +7341,9 @@ in {
 
   python-xmp-toolkit = callPackage ../development/python-modules/python-xmp-toolkit { };
 
-  pythran = callPackage ../development/python-modules/pythran { };
+  pythran = callPackage ../development/python-modules/pythran {
+    inherit (pkgs.llvmPackages) openmp;
+  };
 
   pyeverlights = callPackage ../development/python-modules/pyeverlights { };