7.x - Upgrade to Gradle 8 - set source/target compatibility to Java 17

[codeconsole]

The 7.x branch should be running on Gradle 8.x with a min source/target compatibility of Java 17

https://docs.gradle.org/current/userguide/compatibility.html

https://github.com/orgs/grails/projects/3/views/2?pane=issue&itemId=71425178

[codeconsole]

#290

[codeconsole]

Installing: gradle 8.5
Done installing!

Do you want gradle 8.5 to be set as default? (Y/n): n
grails-gradle-plugin % gradle clean assemble 

> Task :compileGroovy FAILED
startup failed:
/grails-gradle-plugin/src/main/groovy/org/grails/gradle/plugin/web/gsp/GspCompileOptions.groovy: 21: You cannot create an instance from the abstract class 'org.gradle.api.tasks.compile.GroovyForkOptions'.
 @ line 21, column 37.
       GroovyForkOptions forkOptions = new GroovyForkOptions()
                                       ^

1 error


FAILURE: Build failed with an exception.

[davydotcom]

GroovyForkOptions is now an abstract class i fixed this already but have a new error (not pushed yet)

> Unrecoverable compilation error: startup failed:
  General error during canonicalization: java.lang.NoClassDefFoundError: org.springframework.boot.loader.tools.LoaderImplementation
  
  java.lang.RuntimeException: java.lang.NoClassDefFoundError: org.springframework.boot.loader.tools.LoaderImplementation

I have this fixed on another machine i'll add the missing dependency in a bit to finish this part