This commit relicenses FuseSoC from GPLv3 to the 2-Clause (or
"Simplified") BSD License. All copyright holders have been contacted,
and they have agreed to this license change.

Motivation: We have had multiple users expressing interest in using
(parts of) FuseSoC as a library. Use cases include FuseSoC generators
which make use of FuseSoC-internal classes, or the integration of
FuseSoC into other build systems. With FuseSoC licensed under the GPLv3,
these users have only a single choice: they must license their code
under GPLv3 as well, something which often isn't possible.

To make FuseSoC usable to more people we are re-licensing the FuseSoC
code base under the 2-clause BSD license. This is the same license we
chose for edalize.