Add check of Binaryen support for sourcemaps

compiler/bin-wasm_of_ocaml/compile.ml

@@ -175,7 +175,11 @@ let optimize ~profile ?sourcemap_file in_file out_file =
 
 let link_and_optimize ~profile ?sourcemap_file runtime_wasm_files wat_file output_file =
   let sourcemap_file =
-    if Sys.command "wasm-merge -osm foo 2> /dev/null" <> 0 then None else sourcemap_file
+    (* Check that Binaryen supports the necessary sourcemaps options (requires
+       version >= 118) *)
+    match sourcemap_file with
+    | Some _ when Sys.command "wasm-merge -osm foo 2> /dev/null" <> 0 -> None
+    | Some _ | None -> sourcemap_file
   in
   let enable_source_maps = Option.is_some sourcemap_file in
   with_intermediate_file (Filename.temp_file "runtime" ".wasm")