8272472: StackGuardPages test doesn't build with glibc 2.34

Backport-of: f77a1a156f3da9068d012d9227c7ee0fee58f571

Author: David Holmes

test/hotspot/jtreg/runtime/StackGuardPages/exeinvoke.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2010, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2010, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -68,8 +68,17 @@ static void handler(int sig, siginfo_t *si, void *unused) {
   longjmp(context, 1);
 }
 
+static char* altstack = NULL;
+
 void set_signal_handler() {
-  static char altstack[SIGSTKSZ];
+  if (altstack == NULL) {
+    // Dynamically allocated in case SIGSTKSZ is not constant
+    altstack = malloc(SIGSTKSZ);
+    if (altstack == NULL) {
+      fprintf(stderr, "Test ERROR. Unable to malloc altstack space\n");
+      exit(7);
+    }
+  }
 
   stack_t ss = {
     .ss_size = SIGSTKSZ,