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

fusl/src/legacy/daemon.c

+#define _GNU_SOURCE
+#include <fcntl.h>
+#include <unistd.h>
+
+int daemon(int nochdir, int noclose)
+{
+        if (!nochdir && chdir("/"))
+                return -1;
+        if (!noclose) {
+                int fd, failed = 0;
+                if ((fd = open("/dev/null", O_RDWR)) < 0) return -1;
+                if (dup2(fd, 0) < 0 || dup2(fd, 1) < 0 || dup2(fd, 2) < 0)
+                        failed++;
+                if (fd > 2) close(fd);
+                if (failed) return -1;
+        }
+
+        switch(fork()) {
+        case 0: break;
+        case -1: return -1;
+        default: _exit(0);
+        }
+
+        if (setsid() < 0) return -1;
+
+        switch(fork()) {
+        case 0: break;
+        case -1: return -1;
+        default: _exit(0);
+        }
+
+        return 0;
+}