Remove thread local attribute of prev_sig_act_SIGSEGV/SIGBUS to allow using custom signal handler from non-main thread since in a thread spawned by embedder, embedder may be unable to call wasm_runtime_init_thread_env to initialize them. And fix the handling of prev_sig_act when its sa_handler is SIG_DFL, SIG_IGN, or a user customized handler.
This folder contains the platform abstract layer for multiple platforms. To support a new platform, you can simply create a new folder here and implement all the APIs defined in include folder.
Refer to port_wamr.md for how to port WAMR to a target platform.