Bump required CMake version
Bump required CMake version

CMake 3.21.4 reports that compatibility with CMake < 2.8.12 will be
removed from a future version of CMake.

CMake 3.0 has new defaults for MACOSX_RPATH. It seems ledger works fine
with them. See CMake Policy CMP0042 for the details.

afh/ledger,ledger/ledger,ledger/ledger,ledger/ledger,afh/ledger,afh/ledger,ledger/ledger,afh/ledger,afh/ledger,ledger/ledger