[rtsan][compiler-rt] Fix ioctl test causing segfault on exit (llvm#151182)

I was observing segfaults at executable exit in the rtsan instrumented
unit tests. Bisecting the offending test led to observing that this test
is not using our safe test fixture for anything involving a file
descriptor. Changing to use the fixture eliminated the segfault on exit.

Author: davidtrevelyan

compiler-rt/lib/rtsan/tests/rtsan_test_interceptors_posix.cpp

@@ -752,8 +752,8 @@ TEST_F(RtsanOpenedFileTest, RewindDieWhenRealtime) {
 }
 #endif
 
-TEST(TestRtsanInterceptors, IoctlDiesWhenRealtime) {
-  auto Func = []() { ioctl(0, FIONREAD); };
+TEST_F(RtsanOpenedFileTest, IoctlDiesWhenRealtime) {
+  auto Func = [this]() { ioctl(GetOpenFd(), FIONREAD); };
   ExpectRealtimeDeath(Func, "ioctl");
   ExpectNonRealtimeSurvival(Func);
 }