[CMake] non default architecture builds

[Jack Kelly]

Alexander Neundorf wrote:
>> Now my question:
>> How can I make cmake look into the lib/pa20_64 or lib/sparcv9 directory
>> instead of the plain lib directory?

After running cmake, can't you do a `make edit_cache` and manually set 
the appropriate cache entries (such as OPENGL_LIBRARIES, 
OPENGL_INCLUDE_DIR)? You might need to turn on advanced mode.

-- Jack