pip: `pip wheel -r ...` does not pass `config_settings`

Description

pip wheel correctly passes config_settings when given a requirement specifier directly, but not when given a requirements file.

Works:

pip wheel --config-settings "setup-args=-Dblas=blas" scipy==1.10.1

Doesn’t work:

echo 'scipy==1.10.1' > r.txt
pip wheel --config-settings "setup-args=-Dblas=blas" -r r.txt

Expected behavior

config_settings are passed when using pip wheel with a requirements file

pip version

23.2.1 (also head and older versions)

Python version

3.8

OS

Linux

How to Reproduce

1. in an environment with gfortran intentionally missing, try to build scipy with pip wheel -r ... and setting setup-args
2. in the error output (due to missing gfortran), confirm whether setup-args propagated to the meson command line

-r case (broken)

pip install --upgrade pip wheel
echo 'scipy==1.10.1' > r.txt
pip wheel --config-settings "setup-args=-Dblas=blas" -r r.txt

direct specifier case

pip install --upgrade pip wheel
pip wheel --config-settings "setup-args=-Dblas=blas" scipy==1.10.1

Output

-r case (broken)

-Dblas is not passed to meson build

+ meson setup --prefix=/usr /tmp/pip-wheel-6j8l4ith/scipy_206aaca2ef1b4369946502a91692a4b9 /tmp/pip-wheel-6j8l4ith/scipy_206aaca2ef1b4369946502a91692a4b9/.mesonpy-oc75antm/build --native-file=/tmp/pip-wheel-6j8l4ith/scipy_206aaca2ef1b4369946502a91692a4b9/.mesonpy-native-file.ini -Ddebug=false -Doptimization=2

direct specifier case

+ meson setup --prefix=/usr /tmp/pip-wheel-jf4yjx_6/scipy_5f743564b93f4f4eaadba75a455c21b7 /tmp/pip-wheel-jf4yjx_6/scipy_5f743564b93f4f4eaadba75a455c21b7/.mesonpy-l963lj1w/build --native-file=/tmp/pip-wheel-jf4yjx_6/scipy_5f743564b93f4f4eaadba75a455c21b7/.mesonpy-native-file.ini -Ddebug=false -Doptimization=2 -Dblas=blas

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