buildroot

make: bump to version 4.0

This commit bumps make to version 4.0. This version now uses fork(),
so it is no longer available on non-MMU platforms, which consequently
works around:

  http://autobuild.buildroot.org/results/2e1/2e1b11ccb501f1ab431c04435be52a6538d035cb/

The glob special options seem to no longer be needed, at least make
4.0 builds fine with both an ARM uClibc toolchain and an ARM glibc
toolchain.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>