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

fusl/arch/sh/src/__set_thread_area.c

+#include "pthread_impl.h"
+#include "libc.h"
+#include "sh_atomic.h"
+#include <elf.h>
+
+/* Also perform sh-specific init */
+
+#define CPU_HAS_LLSC 0x0040
+
+__attribute__((__visibility__("hidden"))) unsigned __sh_atomic_model, __sh_nommu;
+
+int __set_thread_area(void *p)
+{
+        size_t *aux;
+        __asm__ __volatile__ ( "ldc %0, gbr" : : "r"(p) : "memory" );
+#ifndef __SH4A__
+        if (__hwcap & CPU_HAS_LLSC) {
+                __sh_atomic_model = SH_A_LLSC;
+                return 0;
+        }
+#if !defined(__SH3__) && !defined(__SH4__)
+        for (aux=libc.auxv; *aux; aux+=2) {
+                if (*aux != AT_PLATFORM) continue;
+                const char *s = (void *)aux[1];
+                if (s[0]!='s' || s[1]!='h' || s[2]!='2' || s[3]-'0'<10u) break;
+                __sh_atomic_model = SH_A_IMASK;
+                __sh_nommu = 1;
+                return 0;
+        }
+#endif
+        /* __sh_atomic_model = SH_A_GUSA; */ /* 0, default */
+#endif
+        return 0;
+}