Detect SIGKILL-broken builds?

[RalfJung]

In this report, several of the non-spurious regressions were actually spurious with a common theme:

[INFO] [stderr] Caused by:
[INFO] [stderr]   process didn't exit successfully: `rustc --crate-name build_script_build /opt/rustwide/cargo-home/registry/src/github.com-1ecc6299db9ec823/html5ever-0.24.1/build.rs --error-format=json --json=diagnostic-rendered-ansi --crate-type bin --emit=dep-info,link -Cembed-bitcode=no -C debuginfo=2 -C metadata=dad972120d17c4d0 -C extra-filename=-dad972120d17c4d0 --out-dir /opt/rustwide/target/debug/build/html5ever-dad972120d17c4d0 -L dependency=/opt/rustwide/target/debug/deps --extern proc_macro2=/opt/rustwide/target/debug/deps/libproc_macro2-ff51c33add086d10.rlib --extern quote=/opt/rustwide/target/debug/deps/libquote-2ea9689f9474b3f0.rlib --extern syn=/opt/rustwide/target/debug/deps/libsyn-992baf1d96373d81.rlib --cap-lints allow --cap-lints=forbid` (signal: 9, SIGKILL: kill)
[INFO] [stderr] warning: build failed, waiting for other jobs to finish...

This applies to all of the following logs:

• https://crater-reports.s3.amazonaws.com/pr-75585/try%23ffa4a0215752773248fb0f0a8092f1c3e7907e9e/gh/davidcornu.yells-at/log.txt
• https://crater-reports.s3.amazonaws.com/pr-75585/try%23ffa4a0215752773248fb0f0a8092f1c3e7907e9e/gh/riontdev.api-hero-rust/log.txt
• https://crater-reports.s3.amazonaws.com/pr-75585/try%23ffa4a0215752773248fb0f0a8092f1c3e7907e9e/gh/goolord.creepy/log.txt

Maybe crater could detect those as well, like it already detects OOM?

[pietroalbini]

We currently rely on Docker to detect OOMs. If the implementation is not huge I'd love a PR to fix this.