SYSTEM_COMPILER: Rework the logic to allow a 'make test-system-compiler'.

1. Always calculate what the expected values are.
2. Add 'make test-system-compiler' to show all of the computed values vs the wanted values.
3. Extend the .info line to buildkernel/kernel-toolchain/toolchain/_cross-tools.
4. Consolidate all of the logic to one condition.

MFC after: 3 days
Sponsored by: EMC / Isilon Storage Division