Enable ABI suffix for extension module

When installing torchaudio from source `python setup.py install` performs
egg (zip) installation. This causes confusion when building from source for
multiple environments with different Python versions, as `_torchaudio.so`
does not have Python ABI version in its name and importlib cannot find it.

This change fixs this by enableing ABI extension.

squash! Enable ABI suffix for extension module

setup.py

@@ -83,7 +83,7 @@ def run(self):
     packages=find_packages(exclude=["build*", "test*", "torchaudio.csrc*", "third_party*", "build_tools*"]),
     ext_modules=setup_helpers.get_ext_modules(),
     cmdclass={
-        'build_ext': setup_helpers.BuildExtension.with_options(no_python_abi_suffix=True)
+        'build_ext': setup_helpers.BuildExtension,
     },
     install_requires=[pytorch_package_dep]
 )