Fix test for debug runtime.

[vitalybuka]

Summary

If runtime compiled with debug on, main will not be the second frame.

[eugenis]

why is that?
the stack trace is grabbed as soon as we enter any interceptor. There should not be any extra frames.
Moreover, compiler-rt is built w/o frame pointers, so it may not be possible to unwind through its code at all!

test/asan/TestCases/double-free.cc

 int main(int argc, char **argv) {
   char *x = (char*)malloc(10 * sizeof(char));
   memset(x, 0, 10);
   int res = x[argc];
   free(x);
   free(x + argc - 1);  // BOOM
   // CHECK: AddressSanitizer: attempting double-free{{.*}}in thread T0
   // CHECK: #0 0x{{.*}} in {{.*}}free
-  // CHECK: #1 0x{{.*}} in main {{.*}}double-free.cc:[[@LINE-3]]
+  // CHECK: 0x{{.*}} in main {{.*}}double-free.cc:[[@LINE-3]]
   // CHECK: freed by thread T0 here:
   // MALLOC-CTX: #0 0x{{.*}} in {{.*}}free
   // MALLOC-CTX: #1 0x{{.*}} in main {{.*}}double-free.cc:[[@LINE-7]]
   // CHECK: allocated by thread T0 here:
   // MALLOC-CTX: double-free.cc:[[@LINE-12]]
   // CHECK-RECOVER: AddressSanitizer: attempting double-free{{.*}}in thread T0
   // CHECK-RECOVER-NOT: AddressSanitizer CHECK failed:
   return res;
 }