[libcxx] [test] Mark throw_bad_alloc_helper() as [[noreturn]].

[STL_MSFT]

Summary

Mark throw_bad_alloc_helper() as [[noreturn]].

This avoids MSVC /analyze warnings about new returning null, since [[noreturn]] allows the analyzer to see what's happening.

[EricWF]

I don't think all the compilers libc++ tests with support [[noreturn]] yet. I'll commit a similar patch to this though.

[EricWF]

Accepting before closing.
I committed something similar in r273819. Please let me know if it doesn't work.

test/support/count_new.hpp

 #if  TEST_HAS_FEATURE(address_sanitizer) \
   || TEST_HAS_FEATURE(memory_sanitizer) \
   || TEST_HAS_FEATURE(thread_sanitizer)
 #define DISABLE_NEW_COUNT
 #endif
 
 namespace detail
 {
+#if TEST_STD_VER >= 11
+   [[noreturn]]
+#endif
    inline void throw_bad_alloc_helper() {
 #ifndef TEST_HAS_NO_EXCEPTIONS
        throw std::bad_alloc();
 #else
        std::abort();
 #endif
    }
 }