Move local maven repo to root project build dir

This enables having all publications in the same repository, making testing things like the Gradle plugin much easier as a single location needs to be added to a build.

Issue sigstore#414

Signed-off-by: Louis Jacomet <louis@gradle.com>

build-logic/publishing/src/main/kotlin/build-logic.publish-to-tmp-maven-repo.gradle.kts

@@ -14,7 +14,7 @@ val localRepoElements by configurations.creating {
     }
 }
 
-val localRepoDir = layout.buildDirectory.dir("local-maven-repo")
+val localRepoDir = rootProject.layout.buildDirectory.dir("local-maven-repo")
 
 publishing {
     repositories {