[CMake] turning off compile testing

[Josef Karthauser]

> -----Original Message-----
> > We do it this way:
> >
> >      cmake -DCMAKE_CXX_COMPILER_WORKS=1 -DCMAKE_C_COMPILER_WORKS=1
> > -DHAVE_CMAKE_SIZEOF_VOID_P=1 .
> >
> 
> That looks like a bad idea to me....  The void one in particular.  You
> should really be careful about setting stuff like this by hand....
> 

It's a hack granted, but there is no other way of telling CMake to
ignore the compiler - the compiler tests aren't as clean as one might
like, and so fail for some of the compilers that we use.  The
HAVE_CMAKE_SIZEOF_VOID_P variable is used, if I remember correctly, to
determine whether the host environment is 32 or 64 bit in order to
select the correct compiler.  However as we are cross compiling, the
host environment is entirely irrelevant, however without this variable
set cmake persists in trying to work it out.  I'm sure that most of this
pain goes away in the 2.7 release - I'm looking forward to evaluating
the new cross build stuff sometime early next year.

Joe