Fix package installation issues (#180)

- For sdist, fix specifying `data_files=` on each Extension instead of on the package itself
- For sdist, fix headers being given as `data_files=` instead of `headers=`
- For wheels, fix using the avx2 instead of the vanilla package to determine CPU capabilities
    - It was touching avx instructions along the way, causing crashes on M1 macs

First part of fixing #179

glue/python/src/stim/__init__.py

@@ -5,7 +5,7 @@
 compatible instructions. Importing a different one can result in runtime segfaults that crash the python interpreter.
 """
 
-import stim._stim_march_avx2 as _tmp
+import stim._stim_march_polyfill as _tmp
 
 _tmp = _tmp._UNSTABLE_detect_march()
 if _tmp == 'avx2':

setup.py

@@ -35,9 +35,9 @@
 stim_polyfill = Extension(
     'stim._stim_march_polyfill',
     sources=RELEVANT_SOURCE_FILES,
+    headers=HEADER_FILES,
     include_dirs=[pybind11.get_include(), "src"],
     language='c++',
-    data_files=['pyproject.toml'] + HEADER_FILES,
     extra_compile_args=[
         *common_compile_args,
         # I would specify -mno-sse2 but that causes build failures in non-stim code...?
@@ -48,9 +48,9 @@
 stim_sse2 = Extension(
     'stim._stim_march_sse2',
     sources=RELEVANT_SOURCE_FILES,
+    headers=HEADER_FILES,
     include_dirs=[pybind11.get_include(), "src"],
     language='c++',
-    data_files=['pyproject.toml'] + HEADER_FILES,
     extra_compile_args=[
         *common_compile_args,
         '-msse2',
@@ -61,9 +61,9 @@
 stim_avx2 = Extension(
     'stim._stim_march_avx2',
     sources=RELEVANT_SOURCE_FILES,
+    headers=HEADER_FILES,
     include_dirs=[pybind11.get_include(), "src"],
     language='c++',
-    data_files=['pyproject.toml'] + HEADER_FILES,
     extra_compile_args=[
         *common_compile_args,
         '-msse2',
@@ -87,7 +87,7 @@
     long_description_content_type='text/markdown',
     ext_modules=[stim_polyfill, stim_sse2, stim_avx2],
     python_requires='>=3.6.0',
-    data_files=[('', ['glue/python/README.md'])],
+    data_files=[('', ['glue/python/README.md', 'pyproject.toml'])],
     packages=['stim'],
     package_dir={'stim': 'glue/python/src/stim'},
     install_requires=['numpy'],