[CMake] Install without building unittests

[Alexander Neundorf]

On 2019 M03 28, Thu 18:22:03 CET Scott Bloom wrote:
> Just a note, for google later on… 😊
> 
> The default appears to have the variable unset, so it doesn’t show up in the
> list of variables in ccmake or the cmake-gui.
 
> I also added it to my system before any INSTALL command was called.  I don’t
> know if that is necessary, but it does work
 
> SET( CMAKE_SKIP_INSTALL_ALL_DEPENDENCY TRUE )

I'm not sure how that applies to the MSVC generators, but when using 
Makefiles, you can do
make install/fast
which just installs without building.

Alex