Avoid expensive calls to Path.toRealPath() in JRTUtil

Calling Path.toAbsolutePath().normalize() already covers most cases.

Fixes eclipse-jdt#2393

org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/util/JRTUtil.java

@@ -150,7 +150,7 @@ public static JrtFileSystem getJrtSystem(File image, String release) throws IOEx
  */
  public static FileSystem getJrtFileSystem(Path path) throws IOException {
  try {
- FileSystem fs = JRT_FILE_SYSTEMS.computeIfAbsent(path.toRealPath(), p -> {
+ FileSystem fs = JRT_FILE_SYSTEMS.computeIfAbsent(path.toAbsolutePath().normalize(), p -> {
  try {
  return FileSystems.newFileSystem(JRTUtil.JRT_URI, Map.of("java.home", p.toString())); //$NON-NLS-1$
  } catch (IOException e) {
@@ -196,7 +196,7 @@ public static FileSystem getJarFileSystem(Path path) throws IOException {
  public static CtSym getCtSym(Path jdkHome) throws IOException {
  CtSym ctSym;
  try {
- ctSym = ctSymFiles.compute(jdkHome.toRealPath(), (Path x, CtSym current) -> {
+ ctSym = ctSymFiles.compute(jdkHome.toAbsolutePath().normalize(), (Path x, CtSym current) -> {
  if (current == null || !current.getFs().isOpen()) {
  try {
  return new CtSym(x);
@@ -440,7 +440,7 @@ class Jdk {
  public Jdk(File jrt) throws IOException {
  this.path = toJdkHome(jrt);
  try {
- this.release = pathToRelease.computeIfAbsent(this.path.toRealPath(), p -> {
+ this.release = pathToRelease.computeIfAbsent(this.path, p -> {
  try {
  return readJdkReleaseFile(p);
  } catch (IOException e) {
@@ -477,7 +477,7 @@ boolean sameRelease(String other) {
 
  static Path toJdkHome(File jrt) {
  Path home;
- Path normalized = jrt.toPath().normalize();
+ Path normalized = jrt.toPath().toAbsolutePath().normalize();
  if (jrt.getName().equals(JRTUtil.JRT_FS_JAR)) {
  home = normalized.getParent().getParent();
  } else {