[clang][aarch64] Precondition isHomogeneousAggregate on isCXX14Aggregate

MSVC on WoA64 includes isCXX14Aggregate in its definition. This is de-facto
specification on that platform, so match msvc's behaviour.

Fixes: https://bugs.llvm.org/show_bug.cgi?id=47611



Co-authored-by: Peter Waller <peter.waller@arm.com>

Differential Revision: https://reviews.llvm.org/D92751