Fix path for finding relative file

This will hopefully make the windows bot go green.

Change-Id: I88477aab1d9ecffcaf0518a3489b21337cf9b2bd
diff --git a/src/test/java/com/android/tools/r8/retrace/api/RetraceApiBinaryCompatibilityTest.java b/src/test/java/com/android/tools/r8/retrace/api/RetraceApiBinaryCompatibilityTest.java
index 4557036..df7c599 100644
--- a/src/test/java/com/android/tools/r8/retrace/api/RetraceApiBinaryCompatibilityTest.java
+++ b/src/test/java/com/android/tools/r8/retrace/api/RetraceApiBinaryCompatibilityTest.java
@@ -62,7 +62,7 @@
       assertEquals(existing.size(), generated.size());
       assertNotEquals(0, existing.size());
       for (Path classFile : generated) {
-        Path otherClassFile = binaryContents.resolve(classFile);
+        Path otherClassFile = binaryContents.resolve(generatedContents.relativize(classFile));
         assertTrue(Files.exists(otherClassFile));
         assertTrue(TestBase.filesAreEqual(classFile, otherClassFile));
       }