Merge commit '2a2889e130fee6d3c11e506328388afb317626ed'

* commit '2a2889e130fee6d3c11e506328388afb317626ed':
  build: Remove stray duplicate conditional variable declaration

This commit is a noop, there is no duplicate in FFmpeg. we have the
tools rules kept in the root Makefile though (see
802d94c36edcd05b53a56ee359d9559cc4e11597)

Merged-by: Clément Bœsch <cboesch@gopro.com>