On non-FreeBSD systems, installing fido2 fails due to platform_system check for requirement

[LouisStAmour]

• I have searched the issue tracker and believe that this is not a duplicate.

Make sure you run commands with -v flag before pasting the output.

Steps to reproduce

pdm init
pdm add fido2==0.9.1

Actual behavior

On non-FreeBSD (such as Mac or Linux):

% pdm add fido2==0.9.1 -v
Adding packages to default dependencies: fido2
======== Start resolving requirements ========
	fido2==0.9.1
	Adding requirement fido2==0.9.1
	Adding requirement six(from fido2 0.9.1)
	Adding requirement cryptography>=1.5(from fido2 0.9.1)
	Adding requirement uhid-freebsd>=1.2.1; platform_system == "FreeBSD"(from fido2 0.9.1)
Resolving: fido2 0.9.1
	New pin: fido2 0.9.1
======== Ending round 0 ========
Preparing isolated env for PEP 517 build...
Requirement already satisfied: setuptools>=40.8.0 in /usr/local/lib/python3.9/site-packages (from -r /var/folders/tj/wz8q0jmx7_92n64zpvh4kh5h0000gn/T/pdm-build-reqs-a54n8u9g.txt (line 1)) (53.0.0)
Requirement already satisfied: wheel in /usr/local/lib/python3.9/site-packages (from -r /var/folders/tj/wz8q0jmx7_92n64zpvh4kh5h0000gn/T/pdm-build-reqs-a54n8u9g.txt (line 2)) (0.36.2)
running egg_info
writing uhid_freebsd.egg-info/PKG-INFO
writing dependency_links to uhid_freebsd.egg-info/dependency_links.txt
writing top-level names to uhid_freebsd.egg-info/top_level.txt
reading manifest file 'uhid_freebsd.egg-info/SOURCES.txt'
writing manifest file 'uhid_freebsd.egg-info/SOURCES.txt'
Requirement already satisfied: wheel in /usr/local/lib/python3.9/site-packages (from -r /var/folders/tj/wz8q0jmx7_92n64zpvh4kh5h0000gn/T/pdm-build-reqs-qywj_t8e.txt (line 1)) (0.36.2)
running bdist_wheel
running build
running build_ext
building 'uhid_freebsd' extension
creating build
creating build/temp.macosx-11-x86_64-3.9
clang -Wno-unused-result -Wsign-compare -Wunreachable-code -fno-common -dynamic -DNDEBUG -g -fwrapv -O3 -Wall -isysroot /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk -I/usr/local/include -I/usr/local/opt/[email protected]/include -I/usr/local/opt/sqlite/include -I/usr/local/opt/tcl-tk/include -I/usr/local/Cellar/[email protected]/3.9.2_1/Frameworks/Python.framework/Versions/3.9/include/python3.9 -c uhid_freebsd.cpp -o build/temp.macosx-11-x86_64-3.9/uhid_freebsd.o
uhid_freebsd.cpp:15:10: fatal error: 'dev/usb/usb_ioctl.h' file not found
#include <dev/usb/usb_ioctl.h>
         ^~~~~~~~~~~~~~~~~~~~~
1 error generated.
error: command '/usr/bin/clang' failed with exit code 1

Expected behavior

% pdm add kombu==4.6.11 -v
Adding packages to default dependencies: kombu
======== Start resolving requirements ========
	fido2==0.9.1
	Adding requirement fido2==0.9.1
	Adding requirement six(from fido2 0.9.1)
	Adding requirement cryptography>=1.5(from fido2 0.9.1)
Resolving: fido2 0.9.1
	New pin: fido2 0.9.1
======== Ending round 0 ========
...
======== Ending round 2 ========
Finish resolving
======== Resolution Result ========
Stable pins:
  fido2 0.9.1
   six x.x.x
   cryptography x.x.x
Extracting package metadata
🔒 Lock successful
Changes are written to pdm.lock.
Changes are written to pyproject.toml.
Synchronizing working set with lock file: 3 to add, 0 to update, 0 to remove

  Install cryptography x.x.x successful
  Install six x.x.x successful
  Install fido2 0.9.1 successful

🎉 All complete!

Environment Information

# Paste the output of `pdm info && pdm info --env` below:
PDM version:        1.4.0                              
Python Interpreter: /usr/local/bin/python3.9 (3.9.2)   
Project Root:       /tmp/...
{
  "implementation_name": "cpython",
  "implementation_version": "3.9.2",
  "os_name": "posix",
  "platform_machine": "x86_64",
  "platform_release": "20.4.0",
  "platform_system": "Darwin",
  "platform_version": "Darwin Kernel Version 20.4.0: ...",
  "python_full_version": "3.9.2",
  "platform_python_implementaiton": "CPython",
  "python_version": "3.9",
  "sys_platform": "darwin"
}

PDM is ignoring FreeBSD requirement at https://github.com/Yubico/python-fido2/blob/bd72e7aaab08c4e0ebed72fe7cb5f9edd8a32a36/setup.py#L59