Close JarFile when finding main class from archive

MainClassFinder.findSingleMainClass(JarFile, ...) does not close the
JarFile; the caller owns the resource. FindMainClass passed a newly
opened JarFile without closing it, unlike sibling call sites that use
try-with-resources.

See gh-50949

Signed-off-by: Sebastien Tardif <sebtardif@ncf.ca>

Author: SebTardif

build-plugin/spring-boot-antlib/src/main/java/org/springframework/boot/ant/FindMainClass.java

@@ -71,8 +71,9 @@ public void execute() throws BuildException {
 			if (this.classesRoot.isDirectory()) {
 				return MainClassFinder.findSingleMainClass(this.classesRoot, SPRING_BOOT_APPLICATION_CLASS_NAME);
 			}
-			return MainClassFinder.findSingleMainClass(new JarFile(this.classesRoot), "/",
-					SPRING_BOOT_APPLICATION_CLASS_NAME);
+			try (JarFile jarFile = new JarFile(this.classesRoot)) {
+				return MainClassFinder.findSingleMainClass(jarFile, "/", SPRING_BOOT_APPLICATION_CLASS_NAME);
+			}
 		}
 		catch (IOException ex) {
 			throw new BuildException(ex);