Make __asan_handle_no_return a no-op during initialization

Some of our existing tests hang on the new Windows bot with this stack:

770, clang_rt.asan_dynamic-i386.dll!__asan::AsanTSDGet+0x3e
771, clang_rt.asan_dynamic-i386.dll!__asan::GetCurrentThread+0x9
772, clang_rt.asan_dynamic-i386.dll!__asan_handle_no_return+0xe
773, clang_rt.asan_dynamic-i386.dll!__asan_wrap__except_handler4_common+0x12
774, ntdll.dll!wcstombs+0xb0 (No unwind info)
775, ntdll.dll!ZwWow64CallFunction64+0x2001 (No unwind info)
776, ntdll.dll!ZwWow64CallFunction64+0x1fd3 (No unwind info)
777, ntdll.dll!KiUserExceptionDispatcher+0xf (No unwind info)
778, clang_rt.asan_dynamic-i386.dll!destroy_fls+0x13
779, ntdll.dll!RtlLockHeap+0xea (No unwind info)
780, ntdll.dll!LdrShutdownProcess+0x7f (No unwind info)
781, ntdll.dll!RtlExitUserProcess+0x81 (No unwind info)
782, kernel32.dll!ExitProcess+0x13 (No unwind info)
783, clang_rt.asan_dynamic-i386.dll!__sanitizer::internal__exit+0xc
784, clang_rt.asan_dynamic-i386.dll!__sanitizer::Die+0x3d
785, clang_rt.asan_dynamic-i386.dll!__asan::AsanInitInternal+0x50b
786, clang_rt.asan_dynamic-i386.dll!__asan::Allocator::Allocate+0x1c
787, clang_rt.asan_dynamic-i386.dll!__asan::Allocator::Calloc+0x43

We hang because AsanDie tries to defend against multi-threaded death by
infinite looping if someone is already exiting. We might want to
reconsider that, but one easy way to avoid getting here is not to let
our noreturn interceptors call back into fragile parts of ASan.

llvm-svn: 284067