fix build regression in aarch64 sigsetjmp

at least some assembler versions do not accept the register name lr.
use the name x30 instead.

src/signal/aarch64/sigsetjmp.s

@@ -6,7 +6,7 @@ sigsetjmp:
 __sigsetjmp:
 	cbz x1,setjmp
 
-	str lr,[x0,#176]
+	str x30,[x0,#176]
 	str x19,[x0,#176+8+8]
 	mov x19,x0
 
@@ -14,7 +14,7 @@ __sigsetjmp:
 
 	mov w1,w0
 	mov x0,x19
-	ldr lr,[x0,#176]
+	ldr x30,[x0,#176]
 	ldr x19,[x0,#176+8+8]
 
 .hidden __sigsetjmp_tail