fix build files

pyproject.toml

@@ -0,0 +1,3 @@
+[build-system]
+requires = ["setuptools", "wheel", "numpy", "Cython"]
+build-backend = "setuptools.build_meta"

setup.py

@@ -1,36 +1,36 @@
 import os
-
-import numpy
 from setuptools import Extension, find_packages, setup
 
-try:
-    from Cython.Build import cythonize
-
-    ext = ".pyx"
-except ImportError:
-    cythonize = None
-    ext = ".cpp"
 
-ext_modules = [
-    Extension(
-        "ffm.libffm",
-        extra_compile_args=["-Wall", "-O3", "-std=c++0x", "-march=native", "-DUSESSE"],
-        sources=[os.path.join("ffm", "libffm" + ext), "ffm.cpp"],
-        include_dirs=[".", numpy.get_include()],
-        language="c++",
-    )
-]
+def make_extensions():
+    import numpy
+    try:
+        from Cython.Build import cythonize
+        ext = ".pyx"
+    except ImportError:
+        cythonize = None
+        ext = ".cpp"
+    ext_modules = [
+        Extension(
+            "ffm.libffm",
+            extra_compile_args=["-Wall", "-O3", "-std=c++0x", "-march=native", "-DUSESSE"],
+            sources=[os.path.join("ffm", "libffm" + ext), "ffm.cpp"],
+            include_dirs=[".", numpy.get_include()],
+            language="c++",
+        )
+    ]
+    if cythonize is not None:
+        ext_modules = cythonize(ext_modules)
+    return ext_modules
 
-if cythonize is not None:
-    ext_modules = cythonize(ext_modules)
 
 setup(
     name="ffm",
     version="0.4.0",
     description="LibFFM Python Package",
     long_description="LibFFM Python Package",
     install_requires=["numpy"],
-    ext_modules=ext_modules,
+    ext_modules=make_extensions(),
     maintainer="",
     maintainer_email="",
     zip_safe=False,