fix: normalize and replace line separator in node task lock file (#19092)

Normalizes and replaces line separators potentially present in the process
command line before writing the lock file, so that it will contain only two
lines. Same normalization is applied when getting the command line for the
process identified by the pid in the lock file before comparing it with
the value stored in the lock file.

Fixes #19091

Author: mcollovati

flow-server/src/main/java/com/vaadin/flow/server/frontend/NodeTasks.java

@@ -363,7 +363,7 @@ private void getLock() {
                         .of(lockInfo.pid());
 
                 if (processHandle.isPresent()
-                        && processHandle.get().info().commandLine().orElse("")
+                        && normalizeCommandLine(processHandle.get().info())
                                 .equals(lockInfo.commandLine())) {
                     if (!loggedWaiting) {
                         getLogger().info("Waiting for a previous instance of "
@@ -442,11 +442,16 @@ private NodeTasksLockInfo readLockFile()
     private void writeLockFile() throws IOException {
         ProcessHandle currentProcess = ProcessHandle.current();
         long myPid = currentProcess.pid();
-        String commandLine = currentProcess.info().commandLine().orElse("");
+        String commandLine = normalizeCommandLine(currentProcess.info());
         List<String> lines = List.of(Long.toString(myPid), commandLine);
         Files.write(lockFile, lines, StandardCharsets.UTF_8);
     }
 
+    private String normalizeCommandLine(ProcessHandle.Info processInfo) {
+        return processInfo.commandLine()
+                .map(line -> line.replaceAll("\\r?\\n", " \\\\n")).orElse("");
+    }
+
     private Logger getLogger() {
         return LoggerFactory.getLogger(getClass());
     }