tree-sitter: embed path to `emcc` so `tree-sitter build --wasm` works

pkgs/development/tools/parsing/tree-sitter/default.nix

@@ -9,6 +9,7 @@
 , Security
 , callPackage
 , linkFarm
+, substitute
 , CoreServices
 , enableShared ? !stdenv.hostPlatform.isStatic
 , enableStatic ? stdenv.hostPlatform.isStatic
@@ -117,6 +118,13 @@ rustPlatform.buildRustPackage {
     [ which ]
     ++ lib.optionals webUISupport [ emscripten ];
 
+  patches = lib.optionals webUISupport [
+    (substitute {
+      src = ./fix-paths.patch;
+      substitutions = [ "--subst-var-by" "emcc" "${emscripten}/bin/emcc" ];
+    })
+  ];
+
   postPatch = lib.optionalString (!webUISupport) ''
     # remove web interface
     sed -e '/pub mod playground/d' \

pkgs/development/tools/parsing/tree-sitter/fix-paths.patch

@@ -0,0 +1,13 @@
+diff --git a/cli/loader/src/lib.rs b/cli/loader/src/lib.rs
+index 9c1d8dfc..a5cfc74c 100644
+--- a/cli/loader/src/lib.rs
++++ b/cli/loader/src/lib.rs
+@@ -747,7 +747,7 @@ impl Loader {
+             Podman,
+         }
+ 
+-        let emcc_name = if cfg!(windows) { "emcc.bat" } else { "emcc" };
++        let emcc_name = if cfg!(windows) { "emcc.bat" } else { "@emcc@" };
+ 
+         // Order of preference: emscripten > docker > podman > error
+         let source = if !force_docker && Command::new(emcc_name).output().is_ok() {