[libc][NFC] Add new is_trivially_destructible check to libc's type_traits

This patch adds new code to check if a given object is trivially
destructible. The ifdefs where necessary to implement it in gcc, as it
doesn't have the __is_trivially_destructible builtin like clang.

In gcc, it's not enough to only call __has_trivial_destructor, see:
https://stackoverflow.com/questions/20181702/which-type-traits-cannot-be-implemented-without-compiler-hooks

This patch only adds the new check, it will be used in D150211.

Reviewed By: michaelrj, sivachandra

Differential Revision: https://reviews.llvm.org/D158033