package/uboot-tools: needs make >= 4.0

package/uboot-tools: needs make >= 4.0

Starting with 2020.01, uboot started using the 'undefine' make
directive, which was only introduced with make 4.0.

So, use the existing $(BR2_MAKE_HOST_DEPENDENCY) and $(BR2_MAKE),
both of each will ensure that we do use a make that is at least 4.0.

Fixes:
    http://autobuild.buildroot.org/results/c97/c976ed5eb7760cba192d22b3f1e7460596fd82dd/

Reported-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>