If multiple pkgconf entrypoints from different environments are in PATH, they enter a loop trying to call each other

[FFY00]

PS C:\Users\FFY00\Documents\git\numpy> pkg-config scipy-openblas --modversion
> Running the Python pkgconf
> $ PKG_CONFIG_PATH= C:\Users\FFY00\AppData\Local\Programs\Python\Python310\lib\site-packages\pkgconf\.bin\pkgconf.EXE scipy-openblas --modversion
Package scipy-openblas was not found in the pkg-config search path.
Perhaps you should add the directory containing `scipy-openblas.pc'
to the PKG_CONFIG_PATH environment variable
Package 'scipy-openblas', required by 'virtual:world', not found
> Running the system pkgconf.EXE
> $ C:\Users\FFY00\AppData\Local\Programs\Python\Python38-32\Scripts\pkgconf.EXE scipy-openblas --modversion
> Running the Python pkgconf
> $ PKG_CONFIG_PATH= c:\users\ffy00\appdata\local\programs\python\python38-32\lib\site-packages\pkgconf\.bin\pkgconf.EXE scipy-openblas --modversion
Package scipy-openblas was not found in the pkg-config search path.
Perhaps you should add the directory containing `scipy-openblas.pc'
to the PKG_CONFIG_PATH environment variable
Package 'scipy-openblas', required by 'virtual:world', not found
> Running the system pkgconf.EXE
> $ C:\Users\FFY00\AppData\Local\Programs\Python\Python310\Scripts\pkgconf.EXE scipy-openblas --modversion
> Running the Python pkgconf
> $ PKG_CONFIG_PATH= C:\Users\FFY00\AppData\Local\Programs\Python\Python310\lib\site-packages\pkgconf\.bin\pkgconf.EXE scipy-openblas --modversion
Package scipy-openblas was not found in the pkg-config search path.
Perhaps you should add the directory containing `scipy-openblas.pc'
to the PKG_CONFIG_PATH environment variable
Package 'scipy-openblas', required by 'virtual:world', not found
> Running the system pkgconf.EXE
> $ C:\Users\FFY00\AppData\Local\Programs\Python\Python38-32\Scripts\pkgconf.EXE scipy-openblas --modversion
> Running the Python pkgconf
> $ PKG_CONFIG_PATH= c:\users\ffy00\appdata\local\programs\python\python38-32\lib\site-packages\pkgconf\.bin\pkgconf.EXE scipy-openblas --modversion
Package scipy-openblas was not found in the pkg-config search path.
Perhaps you should add the directory containing `scipy-openblas.pc'
to the PKG_CONFIG_PATH environment variable
Package 'scipy-openblas', required by 'virtual:world', not found
(...)

[virtuald]

This also occurs on Linux if you have pkgconf-pypi installed and don't have pkg-config or pkgconf installed on your system.