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

fusl/src/setjmp/x32/longjmp.s

+/* Copyright 2011-2012 Nicholas J. Kain, licensed under standard MIT license */
+.global _longjmp
+.global longjmp
+.type _longjmp,@function
+.type longjmp,@function
+_longjmp:
+longjmp:
+        mov %rsi,%rax           /* val will be longjmp return */
+        test %rax,%rax
+        jnz 1f
+        inc %rax                /* if val==0, val=1 per longjmp semantics */
+1:
+        mov (%rdi),%rbx         /* rdi is the jmp_buf, restore regs from it */
+        mov 8(%rdi),%rbp
+        mov 16(%rdi),%r12
+        mov 24(%rdi),%r13
+        mov 32(%rdi),%r14
+        mov 40(%rdi),%r15
+        mov 48(%rdi),%rdx       /* this ends up being the stack pointer */
+        mov %rdx,%rsp
+        mov 56(%rdi),%rdx       /* this is the instruction pointer */
+        jmp *%rdx               /* goto saved address without altering rsp */