makechrootpkg: keep {SRC,SRCPKG,PKG,LOG}DEST, MAKEFLAGS & PACKAGER values

Kristian Klausenrequested to merge
github/fork/ribbons/makechrootpkg-keep-env-vars into master

Created by: ribbons

If makechrootpkg is called as non-root, the {SRC,SRCPKG,PKG,LOG}DEST, MAKEFLAGS and PACKAGER environment variables are lost in the call to check_root().

Add these to the passed keepenv list so that they are preserved instead.

Merge request reports