poudriere options doesn't respect the "all" flavor

[bsdjhb]

Prerequisites

• [x] Have you checked for an existing issue describing your problem?
• [ ] Are you running the latest version?
• [x] Is your ports tree recent?
• [x] Is your FreeBSD Host on a supported release?

Describe the bug

poudriere options doesn't handle the "all" pseudo flavor correctly but treats it as a literal flavor rather than iterating over all of the ports' available flavors.

How to reproduce

From the log messages sent to stdout, poudriere options devel/freebsd-gcc6@all appears to run make config for the 'all' flavor (see sample output) rather than iterating over the available flavors:

> poudriere options devel/freebsd-gcc6@all
[00:00:00] Appending to make.conf: /usr/local/etc/poudriere.d/make.conf

===> Setting user-specified options for all-gcc6-6.5.0_2 and dependencies

Expected behavior

I would expect poudriere options to iterate over the available flavors for the all pseudo-flavor as it does for other commands like bulk.

Environment

• FreeBSD 13.0 amd64, though I've also seen this on 12.x
• Poudriere Version: 3.3.4 but I've noticed this behavior ever since I added flavors to devel/freebsd-gcc*

[bdrewery]

As far as I can tell make config does not support FLAVOR at all. It all just goes to 1 directory. I think we should fix that in ports and here.