Switch to Ant lib for tar/zip tasks

The commons wrapper we were using didn't support executable files
so Ant seems like the best choice ultimately, even if it has a
lot of features we don't use or need.

initializr-generator/src/test/java/io/spring/initializr/test/generator/ProjectAssert.java

@@ -217,6 +217,13 @@ public class ProjectAssert {
 		return this;
 	}
 
+	public ProjectAssert hasExecutableFile(String... localPaths) {
+		for (String localPath : localPaths) {
+			assertFile(localPath, true);
+		}
+		return this;
+	}
+
 	public ProjectAssert hasNoFile(String... localPaths) {
 		for (String localPath : localPaths) {
 			assertFile(localPath, false);
@@ -231,6 +238,13 @@ public class ProjectAssert {
 		return this;
 	}
 
+	public ProjectAssert assertExecutableFile(String localPath, boolean executable) {
+		File candidate = file(localPath);
+		assertEquals("Invalid  (\"" + executable + "\") for " + localPath, executable,
+				candidate.exists() && candidate.canExecute());
+		return this;
+	}
+
 	private File file(String localPath) {
 		return new File(dir, localPath);
 	}