[CI] Made setup.py more backwards-compatible (#108)

python/setup.py

@@ -82,7 +82,7 @@ class CMakeBuild(build_ext):
         else:
             import multiprocessing
             cmake_args += ["-DCMAKE_BUILD_TYPE=" + cfg]
-            build_args += ["--", f'-j{2*multiprocessing.cpu_count()}']
+            build_args += ["--", '-j' + str(2 * multiprocessing.cpu_count())]
 
         env = os.environ.copy()
         subprocess.check_call(["cmake", self.base_dir] + cmake_args, cwd=self.build_temp, env=env)