get the python version from env (#4729)

sgl-kernel/setup.py

@@ -235,6 +235,12 @@ ext_modules = [
     ),
 ]
 
+
+def get_py_ver():
+    major, minor = sys.version_info[:2]
+    return f"cp{major}{minor}"
+
+
 setup(
     name="sgl-kernel",
     version=_get_version(),
@@ -245,5 +251,5 @@ setup(
         "build_ext": BuildExtension.with_options(use_ninja=True),
         "build_py": CustomBuildPy,
     },
-    options={"bdist_wheel": {"py_limited_api": "cp39"}},
+    options={"bdist_wheel": {"py_limited_api": get_py_ver()}},
 )