facebook/hhvm — pull request #1520 by alexmalyshev (2014-01-09 01:11:51+00:00)
Title: Add CMake support for using clang++ as the C++ compiler

There was a weird issue where CHECK_CXX_SOURCE_COMPILES wouldn't find
clock_gettime under clang++, switching to CHECK_FUNCTION_EXISTS worked
both under clang++ and g++ on Ubuntu 13.10