cython setuptools change output filename

I am using cython to cross-compile external python module. I am using python3.6 on the host and python3.5 on the target. Also I am compiling on x86_64 for target aarch64.

My setup.py looks like:

from distutils.core import setup
from distutils.extension import Extension
from Cython.Build import cythonize
from Cython.Distutils import build_ext
import builder_config
import os

os.environ["PATH"] = builder_config.PATH
os.environ["CC"] = builder_config.COMPILER
os.environ["LDSHARED"] = builder_config.COMPILER + " -lpython3.5m -shared"
os.environ["CFLAGS"] = builder_config.CFLAGS
os.environ["LDFLAGS"] = builder_config.LDFLAGS
os.environ["ARCH"] = "aarch64"

setup(
    ext_modules = cythonize((Extension("my_ext", ["file1.pyx", "file2.pyx", "file3.pyx", "file4.pyx", "file5.pyx"]))),
)

When I run python3.6 setup.py build_ext -i I get a file named: my_ext.cpython-36m-x86_64-linux-gnu.so

My problem is that on the target the library will not be loaded unless the name is changed to:

my_ext.cpython-35m-aarch64-linux-gnu.so

How can I change the generated filename?

from cython setuptools change output filename