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

fusl/src/process/vfork.c

Index: fusl/src/process/vfork.c
diff --git a/fusl/src/process/vfork.c b/fusl/src/process/vfork.c
new file mode 100644
index 0000000000000000000000000000000000000000..ac954651b70167cf62fcc498fb34672a0680e384
--- /dev/null
+++ b/fusl/src/process/vfork.c
@@ -0,0 +1,17 @@
+#define _GNU_SOURCE
+#include <unistd.h>
+#include <signal.h>
+#include "syscall.h"
+#include "libc.h"
+
+pid_t __vfork(void)
+{
+	/* vfork syscall cannot be made from C code */
+#ifdef SYS_fork
+	return syscall(SYS_fork);
+#else
+	return syscall(SYS_clone, SIGCHLD, 0);
+#endif
+}
+
+weak_alias(__vfork, vfork);