ARC: clone: Ensure that @fn returns back to clone

This showed up due to longstanding test/unistd/clone failure where post
clone, the callback was not exiting and rather falling thru in into main
program.

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

libc/sysdeps/linux/arc/clone.S

@@ -49,8 +49,8 @@ ENTRY(clone)
 	blt	.L__sys_err2	; < 0 (signed) error
 	jnz	[blink]		; Parent returns
 
-	; child jumps off to @fn with @arg as argument
-	j.d	[r10]
+	; child jumps off to @fn with @arg as argument, and returns here
+	jl.d	[r10]
 	mov	r0, r11
 
 	; falls thru to _exit() with result from @fn (already in r0)