Merge pull request #234066 from figsoda/crate

pkgs/build-support/rust/fetchcrate.nix

@@ -2,6 +2,9 @@
 
 { crateName ? args.pname
 , pname ? null
+  # The `dl` field of the registry's index configuration
+  # https://doc.rust-lang.org/cargo/reference/registry-index.html#index-configuration
+, registryDl ? "https://crates.io/api/v1/crates"
 , version
 , unpack ? true
 , ...
@@ -11,7 +14,7 @@ assert pname == null || pname == crateName;
 
 (if unpack then fetchzip else fetchurl) ({
   name = "${crateName}-${version}.tar.gz";
-  url = "https://crates.io/api/v1/crates/${crateName}/${version}/download";
+  url = "${registryDl}/${crateName}/${version}/download";
 } // lib.optionalAttrs unpack {
   extension = "tar.gz";
 } // removeAttrs args [ "crateName" "pname" "version" "unpack" ])