Installation guide: On WSL, clear /mnt/c stuff from PATH #34889
Description
As seen in https://groups.google.com/g/sage-devel/c/1nYw7-6QSkQ, our configure script fails to notice that some stuff in finds in PATH is not suitable:
configure:7510: found /mnt/c/Strawberry/perl/bin/pkg-config
configure:7522: result: /mnt/c/Strawberry/perl/bin/pkg-config
configure:7547: checking pkg-config is at least version 0.29
...
configure:33252: checking for xml2-config
configure:33275: found /mnt/c/Strawberry/c/bin/xml2-config
configure:33288: result: /mnt/c/Strawberry/c/bin/xml2-config
configure:33305: will use system package and not install SPKG libxml2
...
configure:42387: checking for PRIMESIEVE
configure:42394: $PKG_CONFIG --exists --print-errors "primesieve >= 8.0"
./configure: /mnt/c/Strawberry/perl/bin/pkg-config: perl: bad interpreter: No such file or directory
CC: @dimpase @tobiasdiez
Component: documentation
Author: Matthias Koeppe
Branch/Commit: 80a84d4
Reviewer: Dima Pasechnik
Issue created by migration from https://trac.sagemath.org/ticket/34889