introduce a target to build the kernel of the unikernel HermitCore

[stlankes]

We are developing the unikernel HermitCore, where the kernel is written in Rust and is already supported by the Rust Standard Library. To compile the kernel with the new build flag "-Z build-std", we introduce a new target, which avoids the usage of SSE & AVX within the kernel.

[rust-highfive]

r? @davidtwco

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[rust-highfive]

The job x86_64-gnu-llvm-6.0 of your PR failed (pretty log, raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

2019-11-24T20:15:54.8987372Z ##[command]git remote add origin https://github.com/rust-lang/rust
2019-11-24T20:15:54.9159600Z ##[command]git config gc.auto 0
2019-11-24T20:15:54.9226721Z ##[command]git config --get-all http.https://github.com/rust-lang/rust.extraheader
2019-11-24T20:15:54.9276474Z ##[command]git config --get-all http.proxy
2019-11-24T20:15:54.9397131Z ##[command]git -c http.extraheader="AUTHORIZATION: basic ***" fetch --force --tags --prune --progress --no-recurse-submodules --depth=2 origin +refs/heads/*:refs/remotes/origin/* +refs/pull/66713/merge:refs/remotes/pull/66713/merge
---
2019-11-24T20:21:36.0731654Z   = note: `#[warn(unused_imports)]` on by default
2019-11-24T20:21:36.0736532Z 
2019-11-24T20:21:45.9640375Z     Finished release [optimized] target(s) in 1m 19s
2019-11-24T20:21:45.9739195Z tidy check
2019-11-24T20:21:46.4733843Z tidy error: /checkout/src/librustc_target/spec/x86_64_unknown_hermit_kernel.rs:7: line longer than 100 chars
2019-11-24T20:21:48.3814502Z some tidy checks failed
2019-11-24T20:21:48.3814594Z Found 485 error codes
2019-11-24T20:21:48.3814669Z Found 0 error codes with no tests
2019-11-24T20:21:48.3814714Z Done!
2019-11-24T20:21:48.3814714Z Done!
2019-11-24T20:21:48.3814744Z 
2019-11-24T20:21:48.3814772Z 
2019-11-24T20:21:48.3815914Z command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/tidy" "/checkout/src" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo" "--no-vendor"
2019-11-24T20:21:48.3816023Z 
2019-11-24T20:21:48.3816043Z 
2019-11-24T20:21:48.3819005Z failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test src/tools/tidy
2019-11-24T20:21:48.3819059Z Build completed unsuccessfully in 0:01:23
2019-11-24T20:21:48.3819059Z Build completed unsuccessfully in 0:01:23
2019-11-24T20:21:48.3869568Z == clock drift check ==
2019-11-24T20:21:48.3897552Z   local time: Sun Nov 24 20:21:48 UTC 2019
2019-11-24T20:21:48.4153390Z   network time: Sun, 24 Nov 2019 20:21:48 GMT
2019-11-24T20:21:48.4153511Z == end clock drift check ==
2019-11-24T20:21:49.7382959Z 
2019-11-24T20:21:49.7471907Z ##[error]Bash exited with code '1'.
2019-11-24T20:21:49.7498217Z ##[section]Starting: Checkout
2019-11-24T20:21:49.7499878Z ==============================================================================
2019-11-24T20:21:49.7499954Z Task         : Get sources
2019-11-24T20:21:49.7499992Z Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

[bjorn3]

Could you use a target specification json file instead? Or does -Zbuild-std not support that yet?

[stlankes]

As far as I know, build-std does not support a json file (https://doc.rust-lang.org/nightly/cargo/reference/unstable.html). I want to build the kernel as follow:

cargo build -Z build-std=core,alloc --target x86_64-unknown-hermit-kernel

[bjorn3]

The docs don't explicitely say that it is not yet allowed.

[stlankes]

I just test a json file and it seems to work. Thanks you for the hint!

Like x86_64_linux_kernel, the PR would help our work. However we are able to use a json file.

[davidtwco]

r? @alexcrichton

[alexcrichton]

@bors: r+

[bors]

📌 Commit 55ce5c0 has been approved by alexcrichton