[CMake] VS2012 builds using v3.1.0 are a lot slower than v2.8.12

[Paul Smith]

On Tue, 2015-01-20 at 16:02 -0500, Paul Smith wrote:
> > I think devenv is used instead of msbuild when the solution has 
> > fortran projects.
> 
> I certainly don't have any Fortran projects--!!

I think I figured it out: on our build servers we don't delete
everything and start over from scratch all the time (only for our
official release builds).

We recently upgraded our cmake from 2.8.12.2 to 3.1.0 and I think that
the systems where we were seeing this problem had CMakeCache.txt files
left over from when we were using CMake 2.8.12.2, and those files had
CMAKE_MAKE_PROGRAM set (we never set it by hand, even back then, but
maybe the older version of cmake added it to the cache on its own?) to
devenv.

Certainly when I went in and looked at CMakeCache.txt that value was set
to "devenv.exe".  If I regenerated the CMakeCache.txt from scratch, it
was no longer set.