bug#57436: Running ./configure from `guix shell -D guix --pure` errors

[Katherine Cox-Buday]

Maxime Devos <maximedevos@telenet.be> writes:

> Maybe ./configure somehow picks up an old g++ from outside the "guix shell"
> environment.

This turned out to be the issue. I discovered my shell startup files were
mis-configured by running `guix shell --pure --check -D guix`. This is
definitely a user error, and my fault, but maybe we should update the manual
to include the `--check` flag?

-- 
Katherine