Compiling 32-bit vs 64-bit project using CMake

Question

How do I specify that CMake should use a different link_directories value depending on whether the target is 32-bit or 64-bit? For example, 32-bit binaries need

Answer 1

For Boost specifically, you should use

FIND_LIBRARY(Boost 1.44 COMPONENTS ...)

Then the CMake variable Boost_LIBRARY_DIRS will contain the correct library path, which has to be set using LINK_DIRECTORIES, e.g.

LINK_DIRECTORIES(${Boost_LIBRARY_DIRS})

The more general case is correctly described in user434507's answer.