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

fusl/arch/arm/src/__aeabi_memclr.c

Index: fusl/arch/arm/src/__aeabi_memclr.c
diff --git a/fusl/arch/arm/src/__aeabi_memclr.c b/fusl/arch/arm/src/__aeabi_memclr.c
new file mode 100644
index 0000000000000000000000000000000000000000..a25306d7a1046067aa444a107f2ce61ac9613722
--- /dev/null
+++ b/fusl/arch/arm/src/__aeabi_memclr.c
@@ -0,0 +1,9 @@
+#include <string.h>
+#include "libc.h"
+
+void __aeabi_memclr(void *dest, size_t n)
+{
+	memset(dest, 0, n);
+}
+weak_alias(__aeabi_memclr, __aeabi_memclr4);
+weak_alias(__aeabi_memclr, __aeabi_memclr8);