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

fusl/include/stddef.h

Index: fusl/include/stddef.h
diff --git a/fusl/include/stddef.h b/fusl/include/stddef.h
new file mode 100644
index 0000000000000000000000000000000000000000..bd753853503d94ca3759b2e451fffb68675e869b
--- /dev/null
+++ b/fusl/include/stddef.h
@@ -0,0 +1,25 @@
+#ifndef _STDDEF_H
+#define _STDDEF_H
+
+#ifdef __cplusplus
+#define NULL 0L
+#else
+#define NULL ((void*)0)
+#endif
+
+#define __NEED_ptrdiff_t
+#define __NEED_size_t
+#define __NEED_wchar_t
+#if __STDC_VERSION__ >= 201112L || __cplusplus >= 201103L
+#define __NEED_max_align_t
+#endif
+
+#include <bits/alltypes.h>
+
+#if __GNUC__ > 3
+#define offsetof(type, member) __builtin_offsetof(type, member)
+#else
+#define offsetof(type, member) ((size_t)( (char *)&(((type *)0)->member) - (char *)0 ))
+#endif
+
+#endif