[Buildroot] [PATCH 0 of 5 v6] dependencies: some improvements

[Thomas De Schampheleire]

As far as I'm concerned, this should be the last version of this patch
series. I think it is clean and complete and has received the necessary review.

Signed-off-by: Thomas De Schampheleire <thomas.de.schampheleire at gmail.com>

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v4: add Acks by ThomasP and update after feedback
v5: add extra patch to fix download problem because dl dir is absent
v6: use $(@D) and line up with latest git