D22676: Provide a more sensible CMAKE_INSTALL_PREFIX default

[Aleix Pol Gonzalez]

apol marked 2 inline comments as done.

REPOSITORY
  R240 Extra CMake Modules

REVISION DETAIL
  https://phabricator.kde.org/D22676

To: apol
Cc: cgiboudeaux, kde-frameworks-devel, kde-buildsystem, LeGast00n, sbergeron, 
bencreasy, michaelh, ngraham, bruns