Merge branch '2.1.x'

Closes gh-18236

Author: snicoll

spring-boot-project/spring-boot-starters/pom.xml

@@ -134,6 +134,13 @@
 					</execution>
 				</executions>
 			</plugin>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-source-plugin</artifactId>
+				<configuration>
+					<forceCreation>true</forceCreation>
+				</configuration>
+			</plugin>
 			<plugin>
 				<groupId>org.basepom.maven</groupId>
 				<artifactId>duplicate-finder-maven-plugin</artifactId>