zephyr: Enable support for RISCV

[carlocaione]

Make libmetal usable also for RISCV targets.

Signed-off-by: Carlo Caione ccaione@baylibre.com

[arnopo]

minor clean-up else LGTM

[edmooring]

Looks good to go.

[edmooring]

Can we add at least a build test to the CI?

[arnopo]

Can we add at least a build test to the CI?

That's a good point! at least we could add build test with RISC compiler in CI.
@carlocaione
I suppose that everything is available to build for RISCV in Zephyr environment
what should be update in Zephyr build sequence to build for RISCV?

[carlocaione]

what should be update in Zephyr build sequence to build for RISCV?

Only one line.

For RISCV64:

cmake . -DWITH_ZEPHYR=on -DBOARD=qemu_riscv64 -DWITH_TESTS=on -Bbuild-zephyr

for RISCV32:

cmake . -DWITH_ZEPHYR=on -DBOARD=qemu_riscv32 -DWITH_TESTS=on -Bbuild-zephyr

[arnopo]

what should be update in Zephyr build sequence to build for RISCV?

Only one line.

For RISCV64:

cmake . -DWITH_ZEPHYR=on -DBOARD=qemu_riscv64 -DWITH_TESTS=on -Bbuild-zephyr

for RISCV32:

cmake . -DWITH_ZEPHYR=on -DBOARD=qemu_riscv32 -DWITH_TESTS=on -Bbuild-zephyr

Thanks!
I sent a related pull request: #195