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

fusl/include/sys/mman.h

+#ifndef _SYS_MMAN_H
+#define _SYS_MMAN_H
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <features.h>
+
+#define __NEED_mode_t
+#define __NEED_size_t
+#define __NEED_off_t
+
+#if defined(_GNU_SOURCE)
+#define __NEED_ssize_t
+#endif
+
+#include <bits/alltypes.h>
+
+#include <bits/mman.h>
+
+void *mmap (void *, size_t, int, int, int, off_t);
+int munmap (void *, size_t);
+
+int mprotect (void *, size_t, int);
+int msync (void *, size_t, int);
+
+int posix_madvise (void *, size_t, int);
+
+int mlock (const void *, size_t);
+int munlock (const void *, size_t);
+int mlockall (int);
+int munlockall (void);
+
+#ifdef _GNU_SOURCE
+#define MREMAP_MAYMOVE 1
+#define MREMAP_FIXED 2
+void *mremap (void *, size_t, size_t, int, ...);
+int remap_file_pages (void *, size_t, int, size_t, int);
+#endif
+
+#if defined(_GNU_SOURCE) || defined(_BSD_SOURCE)
+int madvise (void *, size_t, int);
+int mincore (void *, size_t, unsigned char *);
+#endif
+
+int shm_open (const char *, int, mode_t);
+int shm_unlink (const char *);
+
+#if defined(_LARGEFILE64_SOURCE) || defined(_GNU_SOURCE)
+#define mmap64 mmap
+#define off64_t off_t
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+#endif