Add buildSrc to generated eclipse project

Post process the generated 'spring' eclipse project to include the
buildSrc/src/main/groovy folder.

build.gradle

@@ -660,6 +660,11 @@ configure(rootProject) {
 	apply plugin: "groovy"
 	apply from: "${gradleScriptDir}/jdiff.gradle"
 
+	eclipse.classpath.file.whenMerged { classpath ->
+		classpath.entries.add(0, new org.gradle.plugins.ide.eclipse.model.SourceFolder(
+			"buildSrc/src/main/groovy", null))
+	}
+
 	reference {
 		sourceDir = file("src/reference/docbook")
 		pdfFilename = "spring-framework-reference.pdf"