thread-mgr: Prevent an already detached thread from being detached again (#1487)
thread-mgr: Prevent an already detached thread from being detached again (#1487)

If WASM app has called pthread_detach() to detach a thread, it will be detached again
when thread exits. Attempting to detach an already detached thread may result in crash
in musl-libc. This patch fixes it.
bytecodealliance/wasm-micro-runtime,bytecodealliance/wasm-micro-runtime,bytecodealliance/wasm-micro-runtime,bytecodealliance/wasm-micro-runtime,bytecodealliance/wasm-micro-runtime,bytecodealliance/wasm-micro-runtime,bytecodealliance/wasm-micro-runtime,bytecodealliance/wasm-micro-runtime