Add a validation step that check if a possible baseline problem is found

[laeubi]

Fix #1917

This one builds the aggregator with the current PR compiler version and generates a artifact comparator zip if any differences are found:

[srikanth-sankaran]

Thanks a lot. Will use it next round and share feedback!

[laeubi]

It first needs to be merged though :-)

[srikanth-sankaran]

It first needs to be merged though :-)

And I am hoping next round will not be for several weeks :)

[srikanth-sankaran]

That failure is a known one: #2187

[iloveeclipse]

and generates a artifact comparator zip if any differences are found:

1. Currently it produces 900 MB file, while the SDK build produced 450 MB. Something saved twice?
2. The check succeeds, but shouldn't it fail right now: Verify Eclipse Platform Aggregator Build / build (pull_request) Successful