Do not rebuild Make if Make 4.2.1 is installed

[paulmenzel]

Currently, the only allowed GNU Make version is 4.2.

$ git grep make_version modules/make
modules/make:make_version := 4.2
modules/make:make_dir := make-$(make_version)
modules/make:make_tar := make-$(make_version).tar.bz2

Version 4.2.1 should also be allowed.

$ make --version
GNU Make 4.2.1
Built for x86_64-pc-linux-gnu
Copyright (C) 1988-2016 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

[whohoho]

It would be nice to allow also higher versions of make, make 4.2 and 4.2.1 don't build on debian:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=891365

But the git head does build.

[osresearch]

Having a consistent version of make is nice, although it does introduce an extra stage and complicates the build targets. We could possibly remove the make version check entirely... it was to support an ancient build machine inside a corporate firewall that was on make 3.x and didn't support some of the fancier options.

Are there higher versions right now? ftp.gnu.org lists 4.2.1 from 2016-06-10 as the latest.

[osresearch]

We should definitely update where we fetch make from... This doesn't look legit:

make_url := http://gnu.mirror.constant.com/make/$(make_tar)

[osresearch]

Related to #352 ?

[osresearch]

This should be fixed by the parallel build fix (in that we use the system make if the make is new enough)