build: fix building with Groovy snapshots

- Resolve issues with building using a Groovy snapshot version.
- Explicitly override the Groovy version in the build when requested, as it is now sourced from grails-bom instead of a property.

Author: matrei

build.gradle

@@ -9,23 +9,41 @@ buildscript {
     }
 }
 
+group = 'org.grails'
+version = project.projectVersion
+
 ext {
     isCiBuild = System.getenv('CI')
     isSnapshot = projectVersion.endsWith('-SNAPSHOT')
     isReleaseVersion = !isSnapshot
     excludeUnusedTransDeps = findProperty('excludeUnusedTransDeps')
 }
 
-group = 'org.grails'
-version = project.projectVersion
+String customGroovyVersion = findProperty('groovyVersion') ?: System.getenv('GROOVY_VERSION')
+if (customGroovyVersion) {
+    logger.lifecycle("Using custom Groovy version: $customGroovyVersion")
+}
 
 allprojects {
+
+    if (customGroovyVersion) {
+        configurations.configureEach {
+            resolutionStrategy.eachDependency { DependencyResolveDetails details ->
+                if (details.requested.group == 'org.apache.groovy') {
+                    details.useVersion(customGroovyVersion)
+                }
+            }
+        }
+    }
+
     repositories {
         mavenCentral()
         maven { url = 'https://repo.grails.org/grails/core' }
         // mavenLocal() // Keep, this will be uncommented and used by CI (groovy-joint-workflow)
-        if (findProperty('groovyVersion')?.endsWith('-SNAPSHOT')) {
-            logger.lifecycle('Adding Groovy Snapshot Repo for project: {}, Using Groovy {}', name, findProperty('groovyVersion'))
+        if (customGroovyVersion?.endsWith('-SNAPSHOT')) {
+            // Used for testing locally against the latest snapshot of Groovy
+            // Usage: ./gradlew build -P"groovyVersion=X.X.X-SNAPSHOT"
+            logger.lifecycle('Adding Groovy Snapshot Repo for project: {}, Using Groovy {}', name, customGroovyVersion)
             maven {
                 name = 'ASF Snapshot repo'
                 url = 'https://repository.apache.org/content/repositories/snapshots'