[Cmake] CMake: problems setting CMAKE_COMPILER_IS_GNUCXX

[Peter Vanroose]

My CMake build failed on solaris and HP, seemingly because of 
failure to detect that the compiler is GNU C/C++, although
CMakeOutput.log says: "Determining if the C++ compiler is GNU succeeded"

As a consequence, the non-gcc flags (+Z on HP and -xar on solaris) are
being used in the build, which makes compilation fail.
I'm using gcc 3.4 ; this worked fine until yesterday.

As a consequence, the "Nightly Configure" of vxl failed on those platforms, 
too.  Because of "CMAKE_ROOT not found" !!  Strange.
(My cmake executable resides in $HOME/bin/$platform, not in the build dir
of CMake; it seems that this has to do with the problem, since it helped
to make $HOME/bin/$platform/cmake a symlink instead of a copy.)

As a workaround, I've edited the files CMake/Modules/Platforms/SunOS.cmake
and HP-UX.cmake, commenting out all non-gcc stuff, and then rebuilt CMake 
before reconfiguring (and resubmitting) vxl nightly.


--	Peter.