skaffold should have warnings when using jib builder with --platform flag

[ericzzzzzzz]

• run the following command against a mixed nodes cluster in this sample project https://github.com/ericzzzzzzz/skaffold/tree/main/examples/jib-gradle

skaffold build --platform linux/arm64,linux/amd64 --default-repo=xxxx --namespace xxx

• the build will succeed but the build artifact is an amd64 image, before the base image configured here jib.from.image = 'gcr.io/google-appengine/openjdk:8' in build.gradle file is an amd64 image
• Most likely skaffold will not inspect build.gradle future, so we probably want to show a warning like jib builder is used, --platform flag is ignored

[renzodavid9]

This PR was created to change the behavior from Jib itself. The PR is already merged, we'll need to wait for the next release.

[gsquared94]

fixed in #7831