chore: update nightly to 2021-09-22

[hawkw]

so, per @mystor, the nightly bump works if we switch to linking with GNU ld.

i spent a while struggling with trying to get rust-lld to work by passing the -z nostart-stop-gc argument, but rust-lld claims it doesn't know about that.

after adding this to the target JSON:

    "linker-flavor": "ld.lld",
    "linker": "rust-lld",
    "post-link-args": {
        "ld.lld": [
            "-z nostart-stop-gc"
        ]
    },

i get

 <...massive horrible linker invocation> "--gc-sections" "-z nostart-stop-gc"
  = note: rust-lld: error: unknown -z value:  nostart-stop-gc


error: could not compile `mycelium-kernel` due to previous error

which seems surprising given that

Require -z start-stop-gc, which is available in trunk ld.lld (https://reviews.llvm.org/D96914) and GNU ld newer than 2021-03-01 (https://sourceware.org/bugzilla/show_bug.cgi?id=27451)
(per some random googling i did https://reviews.llvm.org/D96914)

so, whatever, GNU ld works. but it would be nice if we could make rust-lld work again...

[mystor]

    "linker-flavor": "ld.lld",
    "linker": "rust-lld",
    "post-link-args": {
        "ld.lld": [
            "-z nostart-stop-gc"
        ]
    },

Wouldn't you need to write it more like:

"ld.lld": ["-z", "nostart-stop-gc"]

because they need to be passed as separate arguments to the linker? Doing that seems to work for me with rust-lld.

[hawkw]

    "linker-flavor": "ld.lld",
    "linker": "rust-lld",
    "post-link-args": {
        "ld.lld": [
            "-z nostart-stop-gc"
        ]
    },

Wouldn't you need to write it more like:

"ld.lld": ["-z", "nostart-stop-gc"]

because they need to be passed as separate arguments to the linker? Doing that seems to work for me with rust-lld.

ahahahaha cool i'm a dumbass, thanks. nice catch!