--with-system-libmpdec / --with-system-expat still uses the vendored headers #98707
Description
Bug report
Python 3.12.0a1 or the main branch. Run:
$ sudo dnf install mpdecimal-devel expat-devel # or similar for your OS
...
$ git clean -fdx
$ rm -r Modules/_decimal/libmpdec
$ rm -r Modules/expat
$ ./configure --config-cache --enable-shared --with-system-libmpdec --with-system-expat
$ make
...
make: *** No rule to make target 'Modules/_decimal/libmpdec/basearith.h', needed by 'Modules/_decimal/_decimal.o'. Stop.
$ git restore Modules/_decimal/libmpdec
$ make
...
make: *** No rule to make target 'Modules/expat/ascii.h', needed by 'Modules/pyexpat.o'. Stop.
This works fine with Python 3.11.0. I suspect somewhere along #94474 or a similar change, this has changed behavior, but I have not tried bisecting yet.
Your environment
- CPython versions tested on: 3.12.0a1 or the main branch
- Operating system and architecture: Fedora Linux x86_64