Don't modify memory access right when changing data in debug stub.

tests/gdb/gdb_test_guest.c

Index: tests/gdb/gdb_test_guest.c
===================================================================
--- tests/gdb/gdb_test_guest.c	(revision 9590)
+++ tests/gdb/gdb_test_guest.c	(working copy)
@@ -54,6 +54,11 @@
   global_ptr = alloca(arg);
 }
 
+int test_call(int arg) {
+  global_var += arg;
+  return global_var;
+}
+
 int main(int argc, char **argv) {
   assert(argc >= 2);
 
@@ -77,5 +82,10 @@
     test_step_from_function_start(2);
     return 0;
   }
+  if (strcmp(argv[1], "call") == 0) {
+    global_var = 0;
+    test_call(1);
+    return 0;
+  }
   return 1;
 }