SpringBoot Use project.getLayout().getBuildDirectory() instead of project.getBuildDir()

Project.getBuildDir() is deprecated since Gradle 8.3, It will cause Task :spring-boot-project:spring-boot-tools:spring-boot-gradle-plugin:compileJava FAILED

See https://github.com/gradle/gradle/issues/20210

Comment From: quaff

I don't know why those test fails, It fails locally with main branch also.

Comment From: wilkinsona

While I'm happy to merge this, as I have said before you shouldn't be building the project with Gradle 8.3. Please use the wrapper.