So that make commands in the riscv-gnu-toolchain build dir work right.
Otherwise, a make check or make all in work/riscv-gnu-toolchain will build a
newlib toolchain which is confusing.
While this is an SDK for the Freedom U platform, which right now is
RV64GC only, it's also where I've been pointing people who want to build
Linux and a userspace. This patch allows users to change the ISA and
ABI of the target.
Most of the testing effort has been targeted towards RV64GC, but I think
it's good to let people try other targets (and then hopefully fix them
:)).
This now contains the latest toolchain release, along with a our Linux
port applied on top of 4.14-rc8. The toolchain is in good shape: it's
based on stable releases, with every backported patch having landed
upstraem. Linux hasn't landed upstream yet, so while there's been some
review it will get rebased (and archived).
This builds and boots on both Spike and Freedom.
