[DO NOT MERGE] added nix flake

[isubasinghe]

Waiting on adding support for macOS in the nixified compiler here:
https://github.com/isubasinghe/arm-gcc-binutils

[wucke13]

@isubasinghe Please take a look on https://github.com/DLR-FT/seL4-nix-utils. I think I did (almost?) all the work you intend to do here.

[isubasinghe]

Thanks for letting me know @wucke13, in that case I will create some PRs there for anything missing there.

[wucke13]

@isubasinghe Great, I'm looking forward to your contributions 😄. I might suggest you close this PR then, if I understand correctly it will not be pursued further in the near future?

[Ivan-Velickovic]

Suggested change

	"x86_64-linux" "i686-linux" "aarch64-linux" "x86_64-darwin"
	"x86_64-linux" "aarch64-linux" "x86_64-darwin"

[Ivan-Velickovic]

@isubasinghe Great, I'm looking forward to your contributions 😄. I might suggest you close this PR then, if I understand correctly it will not be pursued further in the near future?

I could not find how to get started with https://github.com/DLR-FT/seL4-nix-utils and we need something simple/quick for the Microkit CI so I think I might merge this since it's mostly ready. It's only ~100 lines so I think it's fine to have here on it's own. For building more than just a specific project like the Microkit it seems better to use your approach but this is mainly for CI purposes.

[wucke13]

As you like. If I can be of any help, i.e. explaining the stuff from our repo, please let me know.

Edit:

I could not find how to get started with https://github.com/DLR-FT/seL4-nix-utils

Maybe a short note on that: nix flake show will provide all outputs. Of importance for you is the nix build .#microkit-sdk which would build the sdk and symlink the result to a result symlink in your PWD, or nix develop .#microkit-sdk to get a full development environment including the SDK, cross compiler, bintools and QEMU. For this development environment the MICROKIT_SDK env var is already set to the absolute path where the SDK is located. The microkit-sdk development environment available from nix develop is however based of the binary release of the microkit-sdk from the tutorial for historical reasons. It will eventually be upgrade to the source-built microkit package.

[Ivan-Velickovic]

Thanks @isubasinghe for starting this, I've made #233 to finish it off.