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

fusl/include/byteswap.h

+#ifndef _BYTESWAP_H
+#define _BYTESWAP_H
+
+#include <features.h>
+#include <stdint.h>
+
+static __inline uint16_t __bswap_16(uint16_t __x)
+{
+        return __x<<8 | __x>>8;
+}
+
+static __inline uint32_t __bswap_32(uint32_t __x)
+{
+        return __x>>24 | __x>>8&0xff00 | __x<<8&0xff0000 | __x<<24;
+}
+
+static __inline uint64_t __bswap_64(uint64_t __x)
+{
+        return __bswap_32(__x)+0ULL<<32 | __bswap_32(__x>>32);
+}
+
+#define bswap_16(x) __bswap_16(x)
+#define bswap_32(x) __bswap_32(x)
+#define bswap_64(x) __bswap_64(x)
+
+#endif