Implement individual building of dependencies.
Improve error message when removing a cached package fails due to a missing installation journal.
Implement a first version of a proper build ID computation.

Currently, the build ID is built from a few options that are not strictly necessary to be included (build flags and options) - it would be sufficient to just include the build settings introduced by the selected build type (and would reduce the number of build cache folders).
Fix computation of build settings necessary for linking to library dependencies.