[PATCH] [libcxx] Update the way the -std= flag is chosen by CMake and LibcxxTestFormat

[Marshall Clow]

I would prefer to just drop the whole "c++0x" case. That was a placeholder until c++11 was approved; which happened three years ago.

I'm pretty sure that the LLVM build system just uses "-std=c++11" to build clang.

http://reviews.llvm.org/D4329