Now that speed-dreams-data is available as a submodule, this allows the
build system to choose it for in-tree builds. Therefore, CMake will
perform in the following order:
1. Do not search the speed-dreams-data package if SD_ASSUME_DATADIR is
set.
2. Otherwise, do an in-tree build if the submodule has been updated.
3. Otherwise, search for the speed-dreams-data package on standard
locations and CMAKE_PREFIX_PATH and/or CMAKE_FIND_ROOT_PATH.
4. Otherwise, return an error message.
SD_HAS_DATADIR was rendered redundant, so it has been removed. However,
SD_DATADIR_INSTALL_PREFIX was introduced because it would not equal
SD_DATADIR_ABS for in-tree builds, where an installed version of the
speed-dreams-data package is not required.
In-tree builds now allow to generate NSIS installers with both code and
data.
Xavier Del Campo Romero
880d53d88a
