Fix line endings handling when adding suppression to help mojo

Author: mhalbritter

buildSrc/src/main/java/org/springframework/boot/build/mavenplugin/MavenPluginPlugin.java

@@ -388,13 +388,14 @@ private void save(File output, FileEdit edit) {
 		}
 
 		private String addNullAwaySuppression(String content) {
-			String[] lines = content.split("\n");
+			String separator = System.lineSeparator();
+			String[] lines = content.split(separator);
 			StringBuilder result = new StringBuilder();
 			for (String line : lines) {
 				if (line.startsWith("public class ")) {
-					result.append("@SuppressWarnings(\"NullAway\")").append("\n");
+					result.append("@SuppressWarnings(\"NullAway\")").append(separator);
 				}
-				result.append(line).append("\n");
+				result.append(line).append(separator);
 			}
 			return result.toString();
 		}