Add a "fork" of musl as //fusl.

fusl/src/select/select.c

+#include <sys/select.h>
+#include <signal.h>
+#include <stdint.h>
+#include <errno.h>
+#include "syscall.h"
+#include "libc.h"
+
+int select(int n, fd_set *restrict rfds, fd_set *restrict wfds, fd_set *restrict efds, struct timeval *restrict tv)
+{
+#ifdef SYS_select
+        return syscall_cp(SYS_select, n, rfds, wfds, efds, tv);
+#else
+        syscall_arg_t data[2] = { 0, _NSIG/8 };
+        struct timespec ts;
+        if (tv) {
+                if (tv->tv_sec < 0 || tv->tv_usec < 0)
+                        return __syscall_ret(-EINVAL);
+                time_t extra_secs = tv->tv_usec / 1000000;
+                ts.tv_nsec = tv->tv_usec % 1000000 * 1000;
+                const time_t max_time = (1ULL<<8*sizeof(time_t)-1)-1;
+                ts.tv_sec = extra_secs > max_time - tv->tv_sec ?
+                        max_time : tv->tv_sec + extra_secs;
+        }
+        return syscall_cp(SYS_pselect6, n, rfds, wfds, efds, tv ? &ts : 0, data);
+#endif
+}