[CMake] HOWTO cmake compatiblity?

[Steffen Dettmer]

Hi,

> > > So far I think we need to install cmake into a versionized
> > > directory and invoke it:

I tested with versionized directory and it works really well. For
example when having a symlink

  /opt/toolchain/1.0.0/bin/cmake -> /opt/cmake/3.6.2/bin/cmake

it can be used as:

  $ export PATH=/opt/toolchain/1.0.0/bin/:$PATH
  $ cmake -DCMAKE_TOOLCHAIN_FILE=/opt/toolchain/1.0.0/targets/t1.cmake

Very nice is that then generated files do not depend on PATH,
i.e. when make calls cmake, it calls the initially used cmake by
using the (resolved) full path, in the example /opt/cmake/3.6.2/bin/cmake.

When calling with full path:

  $ /opt/toolchain/1.0.0/bin/cmake \
    -DCMAKE_TOOLCHAIN_FILE=/opt/toolchain/1.0.0/targets/t2.cmake

this full path is used (as it is). Also the correct ctest is
executed by make test.

This is just great, exactly what we need.

Steffen