[CMake] multiple out of source builds from same source

[cimarron_cmake at taylors.org]

Hello, 

I have a situation where I want to produce multiple executables
from the same source code where the different executables would
differ mostly by linking with different external libraries.

If I was using an ordinary makefile, I'd have a slightly different
makefile in each of my destination directories, or I would have
multiple makefiles in my source directory and use make -f to specify
the specific makefile.

I understand that the CMake way of doing things is to have the
CMakeLists.txt file reside in the source directory, but then I can't
effectively have separate setttings in separate CMakeLists.txt files.

So for now I've created what I believe is an unnatural situation 
where I have a directory structure like:

   source/
       settings1/
           CMakeLists.txt  (with settings for build1)
       settings2/
           CMakeLists.txt  (with settings for build2)
   build1
   build2

and I have my build script cd to build1, do a cmake ../source/settings1
then cd to build2, do a cmake ../source/settings2, etc.  The problem
with this is that all my pathnames need an extra level of indirection.

Ideally, I'd like to have something more like

   source/
       settings1-CMakeLists.txt  (with settings for build1)
       settings2-CMakeLists.txt  (with settings for build2)
   build1
   build2

and then do a cmake -f settings1-CMakeLists.txt ../source in build1
and cmake -f settings2-CMakeLists.txt ../source in build2 and so on.

So my questions are:

  1. Is there an equivalent to 'make -f' for CMake?
  2. Is there a better way I can use CMake to accomplish what I want?

I really do want to keep the settings in separate CMake files
instead of using some kind of conditional processing since I have
lots of them which are worked on by different people.

Regards,

Cim