Add single threaded version

wasm/CMakeLists.txt

@@ -31,11 +31,11 @@ if(NOT MUJOCO_WASM_FILES)
     message(FATAL_ERROR "No source files found in codegen/generated/")
 endif()
 
+option(MUJOCO_WASM_THREADS "Build with multi-threading support" ON)
+
 # Set Emscripten linker flags
 set(EMCC_LINKER_FLAGS
     "--bind"
-    "-pthread"
-    "-s PTHREAD_POOL_SIZE=navigator.hardwareConcurrency"
     "-s ASSERTIONS=1"
     "-s ALLOW_MEMORY_GROWTH=1"
     "-s EXPORT_ES6=1"
@@ -48,6 +48,13 @@ set(EMCC_LINKER_FLAGS
     "-g"
     "--emit-tsd mujoco.d.ts"
 )
+if(MUJOCO_WASM_THREADS)
+    list(APPEND EMCC_LINKER_FLAGS
+        "-pthread"
+        "-s PTHREAD_POOL_SIZE=navigator.hardwareConcurrency"
+    )
+    add_definitions(-DMUJOCO_WASM_THREADS)
+endif()
 string (REPLACE ";" " " EMCC_LINKER_FLAGS_STR "${EMCC_LINKER_FLAGS}")
 
 add_executable(mujoco_wasm ${MUJOCO_WASM_FILES})