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

fusl/arch/arm/src/__aeabi_memcpy.c

Index: fusl/arch/arm/src/__aeabi_memcpy.c
diff --git a/fusl/arch/arm/src/__aeabi_memcpy.c b/fusl/arch/arm/src/__aeabi_memcpy.c
new file mode 100644
index 0000000000000000000000000000000000000000..4ae5c7776a1a9bb8bbaee9b67945df4d4d338810
--- /dev/null
+++ b/fusl/arch/arm/src/__aeabi_memcpy.c
@@ -0,0 +1,9 @@
+#include <string.h>
+#include "libc.h"
+
+void __aeabi_memcpy(void *restrict dest, const void *restrict src, size_t n)
+{
+	memcpy(dest, src, n);
+}
+weak_alias(__aeabi_memcpy, __aeabi_memcpy4);
+weak_alias(__aeabi_memcpy, __aeabi_memcpy8);