Brutalist buck2 + cargo rule

BUCK

load("//build-rules/cargo.bzl", "cargo_library")

cargo_library(
  name = "dal",
  package = "dal",
  build_type = "debug",
  srcs = glob(["lib/dal/**/*.rs", "lib/dal/build.rs"]),
  out = "libdal"
)

cargo.bzl

def cargo_library_impl(ctx: "context") -> ["provider"]:
    script = ctx.actions.write("cargo-build.sh", """#!/bin/bash
set -euxo pipefail
cargo build -p $1
mkdir -p $4
cp target/$2/$3.* $4
""", is_executable = True);
    out = ctx.actions.declare_output(ctx.attrs.out, dir = True)
    args = cmd_args([script, ctx.attrs.package, ctx.attrs.build_type, ctx.attrs.out, out.as_output()])
    args.hidden([ctx.attrs.srcs])
    args.hidden([ctx.attrs.deps])
    ctx.actions.run(args, category = "cargo", identifier = "build", local_only = True)
    return [DefaultInfo(default_outputs = [out])]

cargo_library = rule(impl = cargo_library_impl, attrs = {
    "package": attrs.string(doc = "Cargo package name"),
    "srcs": attrs.list(attrs.source(), doc = """List of package.json files to track"""),
    "deps": attrs.list(attrs.source(), default = [], doc="A buck2 dep"),
    "build_type": attrs.string(),
    "out": attrs.string(doc="the basename of the file(s) in target to track as output"),
})