In CMake, if a dependency is not explicitly marked as REQUIRED, then if it's not present the build will continue and try to do... something, in the usual bash script fashion: set all environment variables to an empty string and cross fingers that everything will work anyhow.
This MR therefore proposes to mark every find_package statement whose dependency seems required for the build to succeed as REQUIRED. Whether a dependency is required was determined through the following criteria:
If the CMake script uses the dependency (e.g. by expanding one of the Package_XYZ environment variables or linking to the dep) without checking if it has been found, then the dependency should be required.
If the CMake script does not use the dependency in any obvious way (i.e. calls find_package purely for side-effects), then the dependency should be required as well. Note that this criterion is ambiguous: it may well be that the dependency is not needed at all.
Hadrien Benjamin Grasland authored