[CMake] FindBoost problem when cross-compiling

[ross hennessy]

> In your toolchain file, what do you have
> CMAKE_FIND_ROOT_PATH_MODE_INCLUDE set to? If it is set to ONLY, then
> cmake will only look in the CMAKE_FIND_ROOT_PATH for boost, which is
> probably set to $QNX_TARGET. Since you most likely don't have boost in
> your $QNX_TARGET directory, findBoost will fail. I set it to BOTH in my
> toolchain file, although I'm not sure this is entirely a good idea.

You have been very helpful again. This does indeed solve the problem.

> Alternatively you can copy the boost tree into $QNX_TARGET/usr/include
> or somewhere. Maybe there's a better solution I'm not aware of?

This got me reading on the right track and I found a section in the
cmake cross-compiling documentation at
http://www.vtk.org/Wiki/CMake_Cross_Compiling which mentions that you
should create a directory for additional library dependencies "and add
this to CMAKE_FIND_ROOT_PATH, so the FIND_XXX() commands will search
there too." So I was also able to solve the problem by setting
CMAKE_FIND_ROOT_PATH_MODE_INCLUDE to ONLY and adding $ENV{BOOST_ROOT}
to CMAKE_FIND_ROOT_PATH. I'm happy with this solution as it gives me
more control over where the FIND_PATH is searching (I also don't like
the idea of copying multiple versions of boost to different install
locations for all the required targets).

Thanks, Ross