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

[Brad King]

> As a workaround, I could use symlinks like explained in the ccache
> manual, and use this linked gcc in my CC :
>
>     cp ccache /usr/local/bin/
>     ln -s /usr/local/bin/ccache /usr/local/bin/gcc
>     ln -s /usr/local/bin/ccache /usr/local/bin/cc

CMake supports compilers that are not in the path, so you could do

mkdir ${HOME}/foo
ln -s /usr/bin/ccache ${HOME}/foo/gcc
ln -s /usr/bin/ccache ${HOME}/foo/g++

CC=${HOME}/foo/gcc
CXX=${HOME}/foo/g++

-Brad