man-pages: use env from coreutils-native

man-pages: use env from coreutils-native

This is the outcome of investigating the selftest-armhost fail:
https://autobuilder.yoctoproject.org/typhoon/#/builders/127/builds/3028/steps/15/logs/stdio

When man-pages recipe builds on ubuntu 18.04, /usr/bin/env on that is too
old to support -S option, and the outcome is that man-pages quietly
installs nothing, and no packages get created, and the test
that expects the package to exist fails.

Signed-off-by: Alexander Kanavin <alex@linutronix.de>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>