Update to kotlin 1.4.21

[JeroenMols]

Updated the existing kotlin-1.4 branch with:

• latest version of Kotlin, Coroutines and Serialization
• remove EAP repositories
• remove Kotlin stdlib definitions

I verified this PR by :

• running all conformance tests for jvm, js and macos
• building the code generator using the two gradle commands provided in the readme
• building the runtime library

I didn't publish a build to a local maven repository and run the sample apps using that.

Happy to receive feedback on whether I'm following the right procedures.

[JeroenMols]

test this please

[JeroenMols]

Was worth a shot

The build failed due to a timeout and I'm wary to increase the timeout (I don't have enough insights into this project to make that assessment). Can anyone trigger a new build for me please? Thank you.

[garyp]

Your changes look good and your testing approach sounds good too. The only testing step I would add is to publish the library to your Maven Local repo and try building the example apps against it (if you export CI=true before running Gradle in the sample app directories, the sample app build will look for pbandk in Maven Local).

FYI, you can trigger a new CI build by force pushing a new commit to the branch (e.g. you can do git commit --amend to rewrite the current commit without introducing any code changes). We haven't set up any comment-based CI triggers yet.

I haven't had a chance to pull down your branch and confirm this locally. But I suspect the timeout is the same problem I was seeing with earlier releases of Kotlin 1.4. Something in the pbandk code seems to trigger a bug in the Kotlin compiler and cause it to get into a loop and run indefinitely. Given more time the compiler eventually crashes with a stack overflow or similar memory exhaustion error. I was hoping that 1.4.20 would've fixed the bug but sounds like it hasn't 😞 This only happens with Kotlin 1.4, not Kotlin 1.3.

If you have the time and expertise to dig into this, it'd be great to isolate the code that triggers this condition and file a bug in the Kotlin issue tracker. Either way, this is fine to merge into the kotlin-1.4 branch. We just can't merge it into master until this issue is resolved.

[garyp]

Good news! I had a chance to pull this down and try building it locally and everything works on my laptop too. Which means the CI failure is probably a different problem from the bug we were seeing in earlier Kotlin 1.4 releases. I'll merge this PR into the kotlin-1.4 branch and will try to figure out the CI problem on there. I suspect maybe we just need to up the CPU and/or memory allotment for the CI job so it can run more quickly. Some of the Kotlin MPP compilation tasks are quite resource heavy.