Add -O3 and -march=native to compile flags

The latter is required to make compiler emit bit manipulation CPU instructions.

setup.py

@@ -86,6 +86,7 @@ def build_extensions(self):
         for ext in self.extensions:
             ext.include_dirs.append(self.libcommute_includedir)
             ext.cxx_std = 17
+            ext.extra_compile_args += ["-O3", "-march=native"]
 
         build_ext.build_extensions(self)