The previous PR #890 introduced a `Defaults.mk` target for defining
default variables for future calls to `make`. This functionality was
already present in a different form, but this new "real" target had an
unintended side-effect of causing the target to be called automatically
at reference, even the optional reference `-include Defaults.mk`. This
is undesirable as it causes the generation of defaults even during a
`make clean`.
This commit resolves these issues and further refactors the Makefile,
building on the work in #890, but with additional understanding:
* Convert the `Defaults.mk` target to the "phony" `defaults` target,
preventing automatic generation
* Refactor and split `clean` targets
* Update `cleanvendor` to reflect `OFFLINE_BUILD`, similar to the
`vendor` target
* Move "tools" targets into `Tools.mk`
* Add `ARCH` to `Variables.mk` for architecture-specific actions
Signed-off-by: Jonathon Anderson <janderson@ciq.com>
1047032bae