previous install can cause compilation problems for newer versions

[KrisThielemans]

external packages are installed (by default in INSTALL, and therefore include files in INSTALL/include). This works fine at first build. However, when the include files of one of the external packages get updated, it is possible that the installed versions get found first (as opposed to the include files of the external package), resulting in compilation failures or segmentation faults.

Example:

Boost gets installed in INSTALL/include. STIR as well. STIR's CMakeLists.txt has

include_directories(${Boost_INCLUDE_DIRS})

before adding its own include directory to the compiler path. This is arguably a bug in STIR, but it is possible that other packages have the same problem.

Possible solution

If every package would be installed in its own directory, this problem would not occur. This is somewhat ugly though and means we will need to take care of passing the relevant paths along.

[KrisThielemans]

STIR bug filed in UCL/STIR#85