Under -fno-exceptions TEST_THROW becomes abort / __builtin_abort which returns
void. This causes a type mismatch in the conditional operator when testing the
library in C++98,03,11 modes.
Use a comma operator to workaround this problem.
Differential Revision: https://reviews.llvm.org/D26147
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@285572 91177308-0d34-0410-b5e6-96231b3b80d8