If Magnum and Corrade get installed into the same directory,
target_include_directories() or target_link_libraries() with Corrade
before Magnum will result in the (usually stale) installed Magnum
headers being picked over the local ones. Which is unwanted, so try to
always put the local Magnum include path first.
Tested manually by installing to an arbitrary location and editing
configure.h to contain an #error. That failed for the Text library, and
with these changes it now doesn't fail anymore, but that's not a
guarantee that I managed to fix all such cases.
Vladimír Vondruš