Exhaust Task List Generation

[kamilrakoczy]

Supersede of #227.
Fixes #215

This PR:

• Updates symbiflow and quicklogic toolchain versions.

• Adds symbiflow_a200t toolchain to make env.

• Changes exhaust.py to by default build all possible combinations of board/toolchain/project.

• Adds --only_required parameter to exhaust.py to build only boards that are defined in project.json as required for CI to be green.

• Adds nexys-video board.

• Limits exhaust.py exception message lenght to 300 characters (without this, log from CI weights ~200MB).

[acomodi]

LGTM. Let's wait for CI

[acomodi]

I see in CI that the test combination matrix is generated also for the following tests:

• multiple_tests
• parameter_tests
• seed_tests

I think it might be good to add the --only-prefix parameter when invoking these tests as well.

[acomodi]

LGTM apart from some indentation issues.

I see some constraints that differ among toolchains. I assume there are some incompatibilities among them, It would be good to add a comment in each of the "special" constraints to report what XDC command generates the issue for not having a unique constraint file among all the toolchains.

Let's wait for CI.

[acomodi]

Why is this constraint called arty-yosys-vivado instead of arty.xdc only? I would guess that the same constraint file would not work on other toolchains. If not, I think this can be removed.

[kamilrakoczy]

Yes, I left option, to use toolchain-specific constraint file, if for some reason, same constraint file won't work on all toolchains, but in this case, it was some leftover. I removed this file and updated arty.xdc to work on all toolchains

[acomodi]

Same thing as above. Is this needed for nextpnr-xilinx only and it does not work for other toolchains?

[kamilrakoczy]

Same as above.