[CMake] cmake and stow: differing installation and runtime locations

[Christoph Groth]

Dear cmake experts,

I like to use GNU stow to install self-compiled packages on my system.
For this to work best, I have to be able to specify during package
configuration a different runtime location (the directory prefix the
package will "think" it is installed to) and installation location (the
directory prefix which will be actually used for installation).

This way I can install all the package files under the prefix
$HOME/stow/package-name and then tell stow to make symlinks to the
runtime location (prefix $HOME).

This procedure allows easy removal and replacement of packages.

I was not able to find out how to specify different installation and
runtime locations with cmake.  Any hints are warmly appreciated.

Thanks
Christoph