[crt][test] Make ctor_dtor.c robust if DT_INIT/DT_FINI is disabled

New ports in glibc typically don't define ELF_INITFINI, so
DT_INIT/DT_FINI support is disabled.
(rhel ppc64le likely patches their glibc this way as well.)
musl can disable DT_INIT/DT_FINI via -DNO_LEGACY_INITFINI.

So we cannot guarantee ctor()/dtor() will be printed.

compiler-rt/test/crt/ctor_dtor.c

@@ -3,16 +3,18 @@
 // RUN: %run %t 2>&1 | FileCheck %s
 
 #include <stdio.h>
+#include <stdlib.h>
 
 // Ensure the various startup functions are called in the proper order.
 
 // CHECK: __register_frame_info()
-// CHECK-NEXT: ctor()
-// CHECK-NEXT: main()
-// CHECK-NEXT: dtor()
-// CHECK-NEXT: __deregister_frame_info()
+/// ctor() is here if ld.so/libc supports DT_INIT/DT_FINI
+// CHECK:      main()
+/// dtor() is here if ld.so/libc supports DT_INIT/DT_FINI
+// CHECK:      __deregister_frame_info()
 
 struct object;
+static int counter;
 
 void __register_frame_info(const void *fi, struct object *obj) {
   printf("__register_frame_info()\n");
@@ -24,10 +26,13 @@ void __deregister_frame_info(const void *fi) {
 
 void __attribute__((constructor)) ctor() {
   printf("ctor()\n");
+  ++counter;
 }
 
 void __attribute__((destructor)) dtor() {
   printf("dtor()\n");
+  if (--counter != 0)
+    abort();
 }
 
 int main() {