Use -Xclang -fopenmp with clang

setup.py

@@ -246,18 +246,17 @@ def build_extensions(self):
                 for flag in ext.extra_compile_args:
                     if compiler_has_flag(self.compiler, flag):
                         extra_compile_args.append(flag)
+                    elif "clang" in self.compiler.compiler[0] and flag == "-fopenmp":
+                        # clang does not support -fopenmp, but does support -Xclang -fopenmp
+                        extra_compile_args.append("-Xclang")
+                        extra_compile_args.append("-fopenmp")
+                        # Also adjust libraries as needed
+                        libraries.remove("gomp")
+                        libraries.append("omp")
                     elif flag == "-fopenmp" and "gomp" in libraries:
                         libraries.remove("gomp")
                 ext.extra_compile_args = extra_compile_args
                 ext.libraries = libraries
-        # if the compiler/linker is clang, replace the gomp library with omp
-        if ct == "unix" and "clang" in self.compiler.compiler[0]:
-            for ext in self.extensions:
-                libraries = ext.libraries
-                if "gomp" in libraries:
-                    libraries.remove("gomp")
-                    libraries.append("omp")
-                ext.libraries = libraries
         build_ext.build_extensions(self)