buildRustCrate: fix wasm bins with hyphenated names

These are currently broken because buildRustCrate will try to mv from
an underscored name to a hyphenated name, but will only try to move an
unsuffixed name; rustc generates wasm binaries with a .wasm suffix.

pkgs/build-support/rust/build-rust-crate/lib.sh

@@ -60,7 +60,11 @@ build_bin() {
     --color ${colors} \
 
   if [ "$crate_name_" != "$crate_name" ]; then
-    mv target/bin/$crate_name_ target/bin/$crate_name
+    if [ -f "target/bin/$crate_name_.wasm" ]; then
+      mv target/bin/$crate_name_.wasm target/bin/$crate_name.wasm
+    else
+      mv target/bin/$crate_name_ target/bin/$crate_name
+    fi
   fi
 }
 

pkgs/build-support/rust/build-rust-crate/test/default.nix

@@ -838,6 +838,19 @@ rec {
         ];
       };
 
+      crateWasm32BinHyphens = assertOutputs {
+        name = "wasm32-crate-bin-hyphens";
+        mkCrate = mkCrate pkgsCross.wasm32-unknown-none.buildRustCrate;
+        crateArgs = {
+          crateName = "wasm32-crate-bin-hyphens";
+          crateBin = [ { name = "wasm32-crate-bin-hyphens"; } ];
+          src = mkBin "src/main.rs";
+        };
+        expectedFiles = [
+          "./bin/wasm32-crate-bin-hyphens.wasm"
+        ];
+      };
+
       brotliTest =
         let
           pkg = brotliCrates.brotli_2_5_0 { };