buildRustPackage: Accept `srcs` attribute as well

Add support for building Rust packages that have multiple sources, i.e.,
that use the `srcs` and `sourceRoot` attributes instead of just `src`.

pkgs/build-support/rust/default.nix

@@ -1,5 +1,11 @@
 { stdenv, cacert, git, rustc, cargo, rustRegistry }:
-{ name, src, depsSha256, buildInputs ? [], cargoUpdateHook ? "", ... } @ args:
+{ name, depsSha256
+, src ? null
+, srcs ? null
+, sourceRoot ? null
+, buildInputs ? []
+, cargoUpdateHook ? ""
+, ... } @ args:
 
 let
   fetchDeps = import ./fetchcargo.nix {
@@ -7,7 +13,7 @@ let
   };
 
   cargoDeps = fetchDeps {
-    inherit name src cargoUpdateHook;
+    inherit name src srcs sourceRoot cargoUpdateHook;
     sha256 = depsSha256;
   };
 

pkgs/build-support/rust/fetch-builder.sh

@@ -1,17 +0,0 @@
-source $stdenv/setup
-
-# cargo-fetch needs to write to Cargo.lock, even to do nothing. We
-# create a fake checkout with symlinks and and editable Cargo.lock.
-mkdir copy
-cd copy
-for f in $(ls $src); do
-  ln -s $src/"$f" .
-done
-rm Cargo.lock
-cp $src/Cargo.lock .
-chmod +w Cargo.lock
-
-$fetcher . $out
-
-cd ..
-rm -rf copy

pkgs/build-support/rust/fetchcargo.nix

@@ -1,12 +1,16 @@
 { stdenv, cacert, git, rustc, cargo, rustRegistry }:
-{ name ? "cargo-deps", src, sha256, cargoUpdateHook ? "" }:
+{ name ? "cargo-deps", src, srcs, sourceRoot, sha256, cargoUpdateHook ? "" }:
 
 stdenv.mkDerivation {
   name = "${name}-fetch";
   buildInputs = [ rustc cargo git ];
-  builder = ./fetch-builder.sh;
-  fetcher = ./fetch-cargo-deps;
-  inherit src rustRegistry cargoUpdateHook;
+  inherit src srcs sourceRoot rustRegistry cargoUpdateHook;
+
+  phases = "unpackPhase installPhase";
+
+  installPhase = ''
+    ${./fetch-cargo-deps} . "$out"
+  '';
 
   outputHashAlgo = "sha256";
   outputHashMode = "recursive";