fix: segfault in panic when statically compiled

[PavelBlinnikov]

In the current state of c3c panic in statically compiled binary leads to segfault.

Test code:

module test;

fn int main(String[] args)
{
    std::core::builtin::panic("test1", "test2", "test3", 31337);
    return 0;
}

Compiled with:

c3c build -z "-static"

Reason: segfault happens because dlclose unloads libc.so.6 in static binaries and funcptr given by dlsym is not valid anymore.

c3c/lib/std/os/posix/process.c3

Lines 64 to 73 in e6c9cfe

	void* handle = libc::dlopen("libc.so.6", libc::RTLD_LAZY);
	if (handle)
	{
	BacktraceFn backtrace_fn = libc::dlsym(handle, "backtrace");
	libc::dlclose(handle);
	if (backtrace_fn)
	{
	return backtrace_fn(buffer, size);
	}
	}

Solution: add RTLD_NODELETE to dlopen which does not allow unloading libc.so.6 in dlclose

void* handle = libc::dlopen("libc.so.6", libc::RTLD_LAZY|libc::RTLD_NODELETE);

[lerno]

Thank you!