Fix java compatibility for build-tools-internal

[breskeby]

This was accidentally set to 15.

• should be 11 not 15 taken from the minimumRuntimeVersion file and not from minimumCompilerVersion
• this also fixes the checkstyle ides setup

[elasticmachine]

Pinging @elastic/es-delivery (Team:Delivery)

[Luegg]

👍 this solved the issue for me and I can now import the checkstyle config without error. Thanks a lot!

[mark-vieira]

@breskeby this was purposefully changed to use the compiler java home. The intention there was that since this is "internal" it should just use the same compiler version as Gradle, and that way we can use newer APIs in our build code. In fact #73784 depends on it.

I think the original reported issue about checkstyle is due to the fact that the IDE itself is executing that code and it's using a Java 11 IDE. Maybe we should split that stuff out somehow or throw it into one of the other existing projects that are Java 11 compatible?

[breskeby]

Ah I see. It looked like I accidentally changed that when porting to build tools internal

[breskeby]

I'll revert this and follow up with @Luegg on the origin of his local problem

[breskeby]

reverted

[mark-vieira]

We still need a solution here. I ran into this issue locally.