Global C++11 compatibility. Our build system compiles flex/bison as C++ rather than C, but a few projects add `-x c` to their flags, forcing the compiler to compile them as C. This causes the compiler to reject the global C++ standard flag, so we need to explicitly provide a C standard flag to override it. Bug: 18466763 Change-Id: I49a6aeecf4abc563bd77127778b6d214e3851037