Provide M2E lifecycle mapping metadata for Maven plugin’s build-info goal

Previously, configuring the build-info goal in a pom would result in 
Eclipse reporting an error for the pom as it didn’t know if/when to
execute the build-info goal.

This commit adds lifecycle mapping metadata so that the goal is executed
on incremental builds. This ensures that the contents of the generated
file are kept up-to-date, reflecting the latest build time, etc.

Closes gh-6723

spring-boot-tools/spring-boot-maven-plugin/src/main/resources/META-INF/m2e/lifecycle-mapping-metadata.xml

+<lifecycleMappingMetadata>
+	<pluginExecutions>
+		<pluginExecution>
+			<pluginExecutionFilter>
+				<goals>
+					<goal>build-info</goal>
+				</goals>
+			</pluginExecutionFilter>
+			<action>
+				<execute>
+					<runOnIncremental>true</runOnIncremental>
+					<runOnConfiguration>false</runOnConfiguration>
+				</execute>
+			</action>
+		</pluginExecution>
+	</pluginExecutions>
+</lifecycleMappingMetadata>