fix warning using glibc method

libc/sysdeps/linux/mips/sigaction.c

@@ -73,8 +73,7 @@ int __libc_sigaction (int sig, const struct sigaction *act, struct sigaction *oa
 
 
 #else
-#warning "Yes there is a warning here.  Don't worry about it."
-static void restore (void) asm ("__restore");
+extern void restore (void) asm ("__restore") attribute_hidden;
 
 /* If ACT is not NULL, change the action for SIG to *ACT.
    If OACT is not NULL, put the old action for SIG in *OACT.  */
@@ -120,4 +119,3 @@ int __libc_sigaction (int sig, const struct sigaction *act, struct sigaction *oa
 
 #endif
 weak_alias (__libc_sigaction, sigaction)
-