Explicity set permissions on files in lib of Boot distribution

Previously, only the permissions for the scripts in bin/ were set. The
permissions for the files in lib/ were not explicity set, leaving them
with the same permissions as the source files in Gradle's cache. This
has proven to be a little brittle when building in certain
environments, leading to test failures. It also assumes that the
file permissions in Gradle's cache will be appropriate for entries in
a distribution archive. That may not always be a reasonable assumption
to make.

To avoid the above-described problems, this commit updates the copy
spec that's used to add files to lib/ in the archive so that each
file uses 0644 for its permissions.

Closes spring-projectsgh-14158

Author: wilkinsona

Diff for: spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/plugin/ApplicationPluginAction.java

@@ -66,10 +66,11 @@ public void execute(Project project) {
 						.fromString(loadResource("/windowsStartScript.txt")));
 		project.getConfigurations().all((configuration) -> {
 			if ("bootArchives".equals(configuration.getName())) {
-				distribution.getContents()
-						.with(project.copySpec().into("lib")
-								.from((Callable<FileCollection>) () -> configuration
-										.getArtifacts().getFiles()));
+				CopySpec libCopySpec = project.copySpec().into("lib")
+						.from((Callable<FileCollection>) () -> configuration
+								.getArtifacts().getFiles());
+				libCopySpec.setFileMode(0644);
+				distribution.getContents().with(libCopySpec);
 				bootStartScripts.setClasspath(configuration.getArtifacts().getFiles());
 			}
 		});