Fix recipe for CMake

Hi all,

I made a NewVersion CMake 3.5.1 , but since it's based on the previous
outdated version, the recipe still has reference to:

pre_install() {
    if [ -d "/System/Index" ]
    then
        GrepReplace "$goboIndex" "$target" cmake_install.cmake
    fi
}

It still Compiled ok, but as a result, the new version RecipeLint
complaints about this:
ERROR: Recipe references /System tree explicitly. Use $<gobo
environment variable>.

I have limited knowledge on programming :P
What is the best way to fix this recipe code?