Custom build_ext breaks parallel build/wheel

Bắt đầu với setup.py và tái hiện lỗi bằng python3 setup.py build bdist_wheel, sau đó so sánh lần chạy build_ext ban đầu với lần gọi build_ext trong quá trình bdist_wheel. Công việc hoàn tất khi lệnh này hoàn thành thành công và tạo ra một wheel mà không có lỗi trình biên dịch.

Our build system typically uses setup.py to generate a wheel via bdist_wheel but to speed up compilation of extensions we also explictly call build and pass -j:

python3 ./setup.py build  -j 8 bdist_wheel

This works for 99% of modules but fails with httptools:

running build
running build_py
creating build/lib.linux-aarch64-cpython-312/httptools
copying httptools/_version.py -> build/lib.linux-aarch64-cpython-312/httptools
copying httptools/__init__.py -> build/lib.linux-aarch64-cpython-312/httptools
creating build/lib.linux-aarch64-cpython-312/httptools/parser
copying httptools/parser/errors.py -> build/lib.linux-aarch64-cpython-312/httptools/parser
copying httptools/parser/__init__.py -> build/lib.linux-aarch64-cpython-312/httptools/parser
running egg_info
writing httptools.egg-info/PKG-INFO
writing dependency_links to httptools.egg-info/dependency_links.txt
writing requirements to httptools.egg-info/requires.txt
writing top-level names to httptools.egg-info/top_level.txt
/usr/lib/python3/dist-packages/pbr/git.py:28: UserWarning: pkg_resources is deprecated as an API. See https://setuptools.pypa.io/en/latest/pkg_resources.html. The pkg_resources package is slated for removal as early as 2025-11-30. Refrain from using this package or pin to Setuptools<81.
  import pkg_resources
reading manifest file 'httptools.egg-info/SOURCES.txt'
reading manifest template 'MANIFEST.in'
adding license file 'LICENSE'
writing manifest file 'httptools.egg-info/SOURCES.txt'
copying httptools/parser/cparser.pxd -> build/lib.linux-aarch64-cpython-312/httptools/parser
copying httptools/parser/parser.pyx -> build/lib.linux-aarch64-cpython-312/httptools/parser
copying httptools/parser/python.pxd -> build/lib.linux-aarch64-cpython-312/httptools/parser
copying httptools/parser/url_cparser.pxd -> build/lib.linux-aarch64-cpython-312/httptools/parser
copying httptools/parser/url_parser.pyx -> build/lib.linux-aarch64-cpython-312/httptools/parser
running build_ext
building 'httptools.parser.parser' extension
creating build/temp.linux-aarch64-cpython-312/httptools/parser
building 'httptools.parser.url_parser' extension
creating build/temp.linux-aarch64-cpython-312/vendor/llhttp/src
creating build/temp.linux-aarch64-cpython-312/vendor/http-parser
aarch64-linux-gnu-gcc -fno-strict-overflow -Wsign-compare -DNDEBUG -g -O2 -Wall -fPIC -I/work/ross/build/tmp/work/core2-64-poky-linux/python3-httptools/0.6.4/sources/httptools-0.6.4/vendor/llhttp/include -I/work/ross/build/tmp/work/core2-64-poky-linux/python3-httptools/0.6.4/sources/httptools-0.6.4/vendor/llhttp/src -I/usr/include/python3.12 -c httptools/parser/parser.c -o build/temp.linux-aarch64-cpython-312/httptools/parser/parser.o -O2
aarch64-linux-gnu-gcc -fno-strict-overflow -Wsign-compare -DNDEBUG -g -O2 -Wall -fPIC -I/work/ross/build/tmp/work/core2-64-poky-linux/python3-httptools/0.6.4/sources/httptools-0.6.4/vendor/http-parser -I/usr/include/python3.12 -c httptools/parser/url_parser.c -o build/temp.linux-aarch64-cpython-312/httptools/parser/url_parser.o -O2
aarch64-linux-gnu-gcc -fno-strict-overflow -Wsign-compare -DNDEBUG -g -O2 -Wall -fPIC -I/work/ross/build/tmp/work/core2-64-poky-linux/python3-httptools/0.6.4/sources/httptools-0.6.4/vendor/http-parser -I/usr/include/python3.12 -c vendor/http-parser/http_parser.c -o build/temp.linux-aarch64-cpython-312/vendor/http-parser/http_parser.o -O2
aarch64-linux-gnu-gcc -shared -Wl,-O1 -Wl,-Bsymbolic-functions -Wl,-Bsymbolic-functions -Wl,-z,relro -g -fwrapv -O2 build/temp.linux-aarch64-cpython-312/httptools/parser/url_parser.o build/temp.linux-aarch64-cpython-312/vendor/http-parser/http_parser.o -L/usr/lib/aarch64-linux-gnu -o build/lib.linux-aarch64-cpython-312/httptools/parser/url_parser.cpython-312-aarch64-linux-gnu.so
aarch64-linux-gnu-gcc -fno-strict-overflow -Wsign-compare -DNDEBUG -g -O2 -Wall -fPIC -I/work/ross/build/tmp/work/core2-64-poky-linux/python3-httptools/0.6.4/sources/httptools-0.6.4/vendor/llhttp/include -I/work/ross/build/tmp/work/core2-64-poky-linux/python3-httptools/0.6.4/sources/httptools-0.6.4/vendor/llhttp/src -I/usr/include/python3.12 -c vendor/llhttp/src/api.c -o build/temp.linux-aarch64-cpython-312/vendor/llhttp/src/api.o -O2
aarch64-linux-gnu-gcc -fno-strict-overflow -Wsign-compare -DNDEBUG -g -O2 -Wall -fPIC -I/work/ross/build/tmp/work/core2-64-poky-linux/python3-httptools/0.6.4/sources/httptools-0.6.4/vendor/llhttp/include -I/work/ross/build/tmp/work/core2-64-poky-linux/python3-httptools/0.6.4/sources/httptools-0.6.4/vendor/llhttp/src -I/usr/include/python3.12 -c vendor/llhttp/src/http.c -o build/temp.linux-aarch64-cpython-312/vendor/llhttp/src/http.o -O2
aarch64-linux-gnu-gcc -fno-strict-overflow -Wsign-compare -DNDEBUG -g -O2 -Wall -fPIC -I/work/ross/build/tmp/work/core2-64-poky-linux/python3-httptools/0.6.4/sources/httptools-0.6.4/vendor/llhttp/include -I/work/ross/build/tmp/work/core2-64-poky-linux/python3-httptools/0.6.4/sources/httptools-0.6.4/vendor/llhttp/src -I/usr/include/python3.12 -c vendor/llhttp/src/llhttp.c -o build/temp.linux-aarch64-cpython-312/vendor/llhttp/src/llhttp.o -O2
aarch64-linux-gnu-gcc -shared -Wl,-O1 -Wl,-Bsymbolic-functions -Wl,-Bsymbolic-functions -Wl,-z,relro -g -fwrapv -O2 build/temp.linux-aarch64-cpython-312/httptools/parser/parser.o build/temp.linux-aarch64-cpython-312/vendor/llhttp/src/api.o build/temp.linux-aarch64-cpython-312/vendor/llhttp/src/http.o build/temp.linux-aarch64-cpython-312/vendor/llhttp/src/llhttp.o -L/usr/lib/aarch64-linux-gnu -o build/lib.linux-aarch64-cpython-312/httptools/parser/parser.cpython-312-aarch64-linux-gnu.so

running bdist_wheel
installing to build/bdist.linux-aarch64/wheel
running install
running install_lib
running build_ext
error: don't know how to compile C/C++ code on platform 'posix' with '<distutils.compilers.C.unix.Compiler object at 0xee4af1454c80>' compiler

This behaviour isn't specific to the use of -j, simply doing python3 setup.py build bdist_wheel results in the build failing.