Compilation warnings were reported on mac:
```
core/shared/mem-alloc/ems/ems_gc.c:454:22: warning: passing arguments to 'wasm_runtime_gc_prepare' without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
gct_vm_gc_prepare(NULL);
^
core/shared/mem-alloc/ems/ems_gc.c:466:23: warning: passing arguments to 'wasm_runtime_gc_finalize' without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
gct_vm_gc_finished(NULL);
^
2 warnings generated.
```
As reported in #3500, when debug interpreter is enabled, the classic interpreter
performs a lock operation to read `exec_env->current_status->signal_flag` and
do further handling before fetching next opcode, which makes the interpreter
run slower.
This PR atomic loads the `exec_env->current_status->signal_flag` without mutex
lock when 32-bit atomic load is supported, and only adding lock for further
handling when the signal_flag is WAMR_SIG_SINGSTEP, which improves the
performance.
There's probably a number of other places where the bh_leb_read could be used (e.g. aot loader)
but I'm making the change as small as possible. Further refactoring can be done later.
Fix:
```
wamr/core/iwasm/libraries/libc-builtin/libc_builtin_wrapper.c:20:1:
warning: type of 'wasm_runtime_module_realloc' does not match original declaration [-Wlto-type-mismatch]
wamr/core/iwasm/common/wasm_runtime_common.c:3033:1:
note: return value type mismatch
wamr/core/iwasm/common/wasm_runtime_common.c:3033:1:
note: type 'uint64' should match type 'uint32'
wamr/core/iwasm/common/wasm_runtime_common.c:3033:1:
note: 'wasm_runtime_module_realloc' was previously declared here
wamr/core/iwasm/common/wasm_runtime_common.c:3033:1:
note: code may be misoptimized unless '-fno-strict-aliasing' is used
```
Some host environment may also create an signal alternate stack and access
it after the wasm runtime exits, the runtime should backup the stack info and
restore it before thread exits.
The issue was found in golang:
```
signal 23 received on thread with on signal stack
fatal error: non-Go code disabled signaltstack
```
Add support for the [Zephyr Usermode](https://docs.zephyrproject.org/latest/kernel/usermode/index.html)
to the Zephyr port.
The following changes are applied:
- Fix `signbit`, check if it is defined already and only implement it, if not
- Introduce `sys_mutex` and `sys_sem` in favour of `k_mutex` and `k_sem`, when `CONFIG_USERMODE` is enabled
- Remove the installation of the `_stdout_hook_iwasm()` when `CONFIG_USERMODE` is enabled, otherwise this
causes MPU errors since the std hook is in the kernel space
- Add a thread name for debugging
This allows users to specify llvm command line options, similarly to clang's -mllvm option.
My motivations:
* -debug and friends
* -mtext-section-literals for xtensa
