[Re-re-land] Enforce a policy on supported Gradle, Java, AGP, and KGP versions

[gmackall]

This is a direct revert of (the revert of (the reland of (the policy pr))): #143132.

The only change is:

1. to put a conditional all on one line, because the packages repository has a test that uses an old flutter project to make sure nothing regresses. The old project uses an old gradle version, and the old gradle version bundles an old groovy version, and the old groovy version has a bug where lines that start with && don't always work: https://issues.apache.org/jira/browse/GROOVY-7218 (I enjoy that the revert reason ends up providing another strong justification to go forward with the policy). Also thanks to @reidbaker for pointing out this bug.
2. I also made a slight formatting change to the messages that print when out of the support bounds, which I think looks slightly better.

I tested this with on a branch that included a revert of #142008, and was able to recreate the failure and verify that it was resolved by 1).

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read and followed the Flutter Style Guide, including Features we expect every widget to implement.
• I signed the CLA.
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is test-exempt.
• All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel on Discord.

[reidbaker]

I believe the root cause but if it is easy can you add links to the documentation you used to prove that the legacy test was using a groovy version that has the bug?

[gmackall]

I believe the root cause but if it is easy can you add links to the documentation you used to prove that the legacy test was using a groovy version that has the bug?

I just modified the top level build.gradle in the legacy app to include

task version { 
  doLast {
    println "Gradle version: " + project.getGradle().getGradleVersion()
    println "Groovy version: " + GroovySystem.getVersion()
  }
}

(idea from https://stackoverflow.com/questions/16527384/checking-groovy-version-gradle-is-using)

when I run ./gradlew -q version, I get

Gradle version: 6.7
Groovy version: 2.5.12

And the fix is included in an alpha version of 2.6.0, according to https://issues.apache.org/jira/browse/GROOVY-7218.

I couldn't find any easy documentation explaining the bundled groovy version, but on the compatibility matrix for Gradle 6.7 (the version the legacy project uses), we can see it says tested with 1.5.8-2.5.12, which is all below the fix range.

edit: It looks like gradle also has a built in --v option which also prints the version, (still 2.5.12), so the hack suggested by the stack overflow post isn't needed

[bartekpacia]

✅

third time lucky (hopefully)