nix: link multicall binaries with cargo-xtask

nix/package.nix

@@ -1,6 +1,7 @@
 {
   lib,
   rustPlatform,
+  stdenv,
 }:
 rustPlatform.buildRustPackage (finalAttrs: {
   pname = "eh";
@@ -21,11 +22,28 @@ rustPlatform.buildRustPackage (finalAttrs: {
       ]);
     };
 
+  # xtask doesn't support passing --targe
+  # but nix hooks expect the folder structure from when it's set
+  env.CARGO_BUILD_TARGET = stdenv.hostPlatform.rust.cargoShortTarget;
   cargoLock.lockFile = "${finalAttrs.src}/Cargo.lock";
   enableParallelBuilding = true;
 
+  postInstall = ''
+    # Install required files with the 'dist' task
+    $out/bin/xtask multicall \
+      --bin-dir $out/bin \
+      --main-binary $out/bin/eh
+
+    # The xtask output has been built as a part of the build phase. If
+    # we don't remove it, it'll be linked in $out/bin alongside the actual
+    # binary and populate $PATH with a dedicated 'xtask' command. Remove.
+    rm -rf $out/bin/xtask
+  '';
+
   meta = {
     description = "Ergonomic Nix CLI helper";
     maintainers = with lib.licenses; [NotAShelf];
+    license = lib.licenses.mpl20;
+    mainProgram = "eh";
   };
 })

nix/shell.nix

@@ -4,6 +4,7 @@
   rustfmt,
   clippy,
   cargo,
+  taplo,
   rustPlatform,
 }:
 mkShell {
@@ -13,6 +14,8 @@ mkShell {
     rustfmt
     clippy
     cargo
+
+    taplo
   ];
 
   RUST_SRC_PATH = "${rustPlatform.rustLibSrc}";