[Thomas:
- replicate the ffmpeg "depends on" related to the broken NIOS2
toolchains to the BR2_PACKAGE_SQUEEZELITE_FFMPEG option.
- use the github helper function.
- add hash file.]
Signed-off-by: Hiroshi Kawashima <kei-k@ca2.so-net.ne.jp>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>