[CMake] looking for Visual Studio installation

[John Drescher]

>> I guess multiple installations of VS is a very rare case.
>
> I pretty much doubt that, making sure a piece of software builds on
> different compilers is important for _anybody_ producing some kind of
> library thats being used by other software components.
>
> Where I work, everybody who has a win32 installation for working on our
> software has at least 2 VS installations. (though we don't use cmake at
> all, but our buildsystem also relies on properly setup environment)
>
One reason for us having more than one version of Visual C++ after the
fact that it cost us no more to have both installed (except for 2 to 4
GB on a 500 to 750GB drive that is worth $50 to $75US with todays sata
prices) is that each version is not 100% backwards compatible and it
sometimes takes a lot of work to port your code base to the next
compiler version. At work I have written 500,000 lines of MFC (about
50,000 lines per year). Most of this was with VC6 however a few years
back I spent over 1 month getting around 80% of this to compile with
VS 2003. Since then I have not taken the time to update that to a
newer compiler. My new projects are now using VS 2005. So I absolutely
need to have VC6, VS2003 and VS2005 installed at minimum. I do have
VS2008 installed as well but I do not use it yet because doing so
would make me have to install that on any developers machine that
would need to use my code...

John