crate_universe: Allow passing extra args down to crate_universe_boots…

…trap (#2279)

this is useful for rules_nixpkgs which allows us to specify an external
rust toolchain controlled by Nix. Currently, we are required to carry a
patch to modify rules_rust:
https://github.com/tweag/rules_nixpkgs/tree/master/examples/toolchains/rust

Now we can add something like this to our WORKSPACE to use a custom
cargo and rustc:
```
crate_universe_dependencies(
    bootstrap = True,
    rust_toolchain_cargo_template = "@nix_rust//:bin/{tool}",
    rust_toolchain_rustc_template = "@nix_rust//:bin/{tool}",
)
```

---------

Co-authored-by: UebelAndre <github@uebelandre.com>

crate_universe/repositories.bzl

@@ -7,17 +7,18 @@ load("//crate_universe/3rdparty/crates:crates.bzl", _vendor_crate_repositories =
 load("//crate_universe/private:vendor_utils.bzl", "crates_vendor_deps")
 load("//crate_universe/tools/cross_installer:cross_installer_deps.bzl", "cross_installer_deps")
 
-def crate_universe_dependencies(rust_version = rust_common.default_version, bootstrap = False):
+def crate_universe_dependencies(rust_version = rust_common.default_version, bootstrap = False, **kwargs):
     """Define dependencies of the `cargo-bazel` Rust target
 
     Args:
         rust_version (str, optional): The version of rust to use when generating dependencies.
         bootstrap (bool, optional): If true, a `cargo_bootstrap_repository` target will be generated.
+        **kwargs: Arguments to pass through to cargo_bazel_bootstrap.
     """
     third_party_deps()
 
     if bootstrap:
-        cargo_bazel_bootstrap(rust_version = rust_version)
+        cargo_bazel_bootstrap(rust_version = rust_version, **kwargs)
 
     _vendor_crate_repositories()
 

docs/crate_universe.md

@@ -720,7 +720,7 @@ A macro for defining repositories for all generated crates
 ## crate_universe_dependencies
 
 <pre>
-crate_universe_dependencies(<a href="#crate_universe_dependencies-rust_version">rust_version</a>, <a href="#crate_universe_dependencies-bootstrap">bootstrap</a>)
+crate_universe_dependencies(<a href="#crate_universe_dependencies-rust_version">rust_version</a>, <a href="#crate_universe_dependencies-bootstrap">bootstrap</a>, <a href="#crate_universe_dependencies-kwargs">kwargs</a>)
 </pre>
 
 Define dependencies of the `cargo-bazel` Rust target
@@ -732,6 +732,7 @@ Define dependencies of the `cargo-bazel` Rust target
 | :------------- | :------------- | :------------- |
 | <a id="crate_universe_dependencies-rust_version"></a>rust_version |  The version of rust to use when generating dependencies.   |  `"1.74.0"` |
 | <a id="crate_universe_dependencies-bootstrap"></a>bootstrap |  If true, a <code>cargo_bootstrap_repository</code> target will be generated.   |  `False` |
+| <a id="crate_universe_dependencies-kwargs"></a>kwargs |  Arguments to pass through to cargo_bazel_bootstrap.   |  none |
 
 
 <a id="render_config"></a>