fix: properly skip docker builds of skipped builds (#4747)

refs https://github.com/orgs/goreleaser/discussions/4469 closes
https://github.com/goreleaser/goreleaser/issues/4746

Also made the error better, and added more details to the docs.

www/docs/customization/docker.md

@@ -68,6 +68,12 @@ dockers:
     goamd64: "v2"
 
     # IDs to filter the binaries/packages.
+    #
+    # Make sure to only include the IDs of binaries you want to `COPY` in your
+    # Dockerfile.
+    #
+    # If you include IDs that don't exist or are not available for the current
+    # architecture being built, the build of the image will be skipped.
     ids:
       - mybuild
       - mynfpm