Set auth credentials when present to autheticate with Spring libs-snapshot Repository.

build.gradle

@@ -7,7 +7,15 @@ buildscript {
 		mavenCentral()
 		gradlePluginPortal()
 		maven { url 'https://repo.spring.io/release' }
-		maven { url 'https://repo.spring.io/plugins-snapshot' }
+		maven {
+			url 'https://repo.spring.io/plugins-snapshot'
+			if (project.hasProperty('artifactoryUsername')) {
+				credentials {
+					username "$artifactoryUsername"
+					password "$artifactoryPassword"
+				}
+			}
+		}
 	}
 }