Revert "Build fontconfig with --with-cache-dir."
The commit breaks the build, as fontconfig's configure scripts don't seem to be able to handle '~' in the '--with-cache-dir' arguments. Alternatively using ${HOME} instead actually works, but a) Bockbuild's own macro expansion rules try to expand ${HOME} and b) cache-dir with ${HOME} seems to be expanded at build-time which I do not think was the idea for this change. Will discuss with @duncanmak and @kumpera.

This reverts commit 0aac9b0881029bff125e11ae4bc7e4c223f828da.