[Feature]: illumos support

Feature Summary

Add illumos as a compilation platform

What problem does this feature solve?

Running Miniflux in an illumos (OmniOS) zone.

Proposed Solution

Go (1.26.5 in my case) supports illumos/amd64 as a target. Just to test if this would work at all, I simply added a stanza to the v2.3.3 Makefile:

illumos-amd64:
	@ CGO_ENABLED=0 GOOS=illumos GOARCH=amd64 go build -ldflags=$(LD_FLAGS) -o $(APP)-$@
	@ sha256sum $(APP)-$@ > $(APP)[email protected]

I did have to use GNU make (gmake) instead of illumos make, but compilation succeeded with no errors and the binary runs fine. I've been running an instance for a couple weeks now without issue.

Alternatives Considered

No response

Additional Context

Although adjusting the Makefile to add a target is trivial here, I did not submit it as a PR because it's not currently possible to run the tests. I am very far from an expert, but this appears to be a Go limitation:

root@web:~/v2-2.3.3# gmake test
go test -cover -race -count=1 ./...
-race is not supported on illumos/amd64
gmake: *** [Makefile:107: test] Error 2

Checklist

• I have searched existing issues to ensure this feature hasn't been requested before.
• I understand that feature requests are not guaranteed to be implemented.
• I agree to follow the project's contribution guidelines.