Change how desugar finds desugared classes to have it working on Windows

RELNOTES: Change how desugar finds desugared classes to have it working on Windows

--
PiperOrigin-RevId: 149738279
MOS_MIGRATED_REVID=149738279

src/tools/android/java/com/google/devtools/build/android/desugar/LambdaClassMaker.java

diff --git a/src/tools/android/java/com/google/devtools/build/android/desugar/LambdaClassMaker.java b/src/tools/android/java/com/google/devtools/build/android/desugar/LambdaClassMaker.java
index ef87407..d8f2e28 100644
--- a/src/tools/android/java/com/google/devtools/build/android/desugar/LambdaClassMaker.java
+++ b/src/tools/android/java/com/google/devtools/build/android/desugar/LambdaClassMaker.java
@@ -24,7 +24,6 @@
 import java.util.ArrayList;
 import java.util.LinkedHashMap;
 import java.util.Map;
-import java.util.function.Function;
 import java.util.function.Predicate;
 import java.util.stream.Stream;
 
@@ -64,23 +63,22 @@
     return result;
   }
 
-  private Path findOnlyUnprocessed(final String pathPrefix) throws IOException {
+  private Path findOnlyUnprocessed(String pathPrefix) throws IOException {
+    // pathPrefix is an internal class name prefix containing '/', but paths obtained on Windows
+    // will not contain '/' and searches will fail.  So, construct an absolute path from the given
+    // string and use its string representation to find the file we need regardless of host
+    // system's file system
+    final String rootPathPrefixStr = rootDirectory.resolve(pathPrefix).toString();
+
     // TODO(kmb): Investigate making this faster in the case of many lambdas
     // TODO(bazel-team): This could be much nicer with lambdas
     try (Stream<Path> results =
         Files.walk(rootDirectory)
-            .map(
-                new Function<Path, Path>() {
-                  @Override
-                  public Path apply(Path path) {
-                    return rootDirectory.relativize(path);
-                  }
-                })
             .filter(
                 new Predicate<Path>() {
                   @Override
                   public boolean test(Path path) {
-                    return path.toString().startsWith(pathPrefix)
+                    return path.toString().startsWith(rootPathPrefixStr)
                         && !generatedClasses.containsKey(path);
                   }
                 })) {