signal.c: static literal string

* signal.c (sigsegv): make message string static to suppress
  unnecessary copy.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@44714 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

signal.c

@@ -691,7 +691,7 @@ sigsegv(int sig SIGINFO_ARG)
 {
     if (segv_received) {
 	ssize_t RB_UNUSED_VAR(err);
-	char msg[] = "SEGV received in SEGV handler\n";
+	static const char msg[] = "SEGV received in SEGV handler\n";
 
 	err = write(2, msg, sizeof(msg));
 	ruby_abort();