Shadow doesn't recognise application's new mainClass property

[BomBardyGamer]

Please check the User Guide before submitting "how do I do 'x'?" questions!

Shadow Version

6.1.0

Gradle Version

7.0

Expected Behavior

shadowJar recognises the new mainClass property (replaces the old mainClassName string field) and uses it appropriately

Actual Behavior

shadowJar errors out because it can't find the value for the mainClassName property

Gradle Build Script(s)

https://pastebin.com/TJWFV78p (you can see if I comment out the old property and set the new property, it doesn't work)

Content of Shadow JAR (jar tf <jar file> - post link to GIST if too long)

N/A

[boris-petrov]

@BomBardyGamer - this is a duplicate of #645, #631, #609, #612.