WIP: Progress on Parallel startup; Fix CI

A new algorithm for dependency resolution which resolves by groups,
allowing for a naive form of parallel startup.

Just added a .cargo/ with a cargo configuration specifying the linker
for x86_64-unknown-redox.
2 jobs for dependencies in 2 minutes and 23 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Build
failed #7856
allowed to fail
build:linux:cargo

00:01:43

passed #7857
build:redox:cargo

00:02:23

 
Name Stage Failure
failed
build:linux:cargo Build

error: aborting due to 6 previous errors

For more information about this error, try `rustc --explain E0308`.
error: Could not compile `init`.

Caused by:
process didn't exit successfully: `rustc --crate-name init src/main.rs --color never --crate-type bin --emit=dep-info,link -C debuginfo=2 -C metadata=34dfbc0deb97ec38 -C extra-filename=-34dfbc0deb97ec38 --out-dir /builds/redox-os/init/target/debug/deps -C incremental=/builds/redox-os/init/target/debug/incremental -L dependency=/builds/redox-os/init/target/debug/deps --extern failure=/builds/redox-os/init/target/debug/deps/libfailure-266c66a4888ff9a1.rlib --extern generational_arena=/builds/redox-os/init/target/debug/deps/libgenerational_arena-8453f0e467056964.rlib --extern log=/builds/redox-os/init/target/debug/deps/liblog-9748a47273ddac59.rlib --extern rayon=/builds/redox-os/init/target/debug/deps/librayon-32b8a108aed66d07.rlib --extern syscall=/builds/redox-os/init/target/debug/deps/libsyscall-6eaad5476c903625.rlib --extern serde=/builds/redox-os/init/target/debug/deps/libserde-c8c1b9e8676cd7dd.rlib --extern serde_derive=/builds/redox-os/init/target/debug/deps/libserde_derive-b39ee62f86d26bf2.so --extern simple_logger=/builds/redox-os/init/target/debug/deps/libsimple_logger-e97d57b34f762821.rlib --extern toml=/builds/redox-os/init/target/debug/deps/libtoml-12105bd257e16158.rlib -L native=/builds/redox-os/init/target/debug/build/backtrace-sys-20d7c04f5674f6ca/out` (exit code: 1)
ERROR: Job failed: exit code 1