[Cmake] pb when CC="ccache gcc" (on linux)

[Brad King]

> I can no longer use the CC and CXX environment variables with a compiler
> name being splitted in several words. This is typically useful when
> using a cache compiler, like http://ccache.samba.org. You define your
> compiler name as CC="ccache gcc".

Try setting

CC=ccache
CXX=ccache
CFLAGS=gcc
CXXFLAGS=g++

-Brad