Normalize line endings in RewindingTestsHelper.buildAndGetOutput

Genrule output files may contain mixed line endings: source files
written by testCase.write() use System.lineSeparator(), but echo in
the genrule command always produces \n. On platforms where the system
line separator is \r\n, this causes buildAndGetOutput assertions to
fail with "line contents match, but line-break characters differ".

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: fmeum

src/test/java/com/google/devtools/build/lib/skyframe/rewinding/RewindingTestsHelper.java

@@ -337,7 +337,9 @@ final String buildAndGetOutput(String pkg, BuildIntegrationTestCase testCase) th
           return ExecResult.delegate();
         });
     testCase.buildTarget(String.format("//%s:consume_output", pkg));
-    return invocationOutput.get();
+    // Genrule output may have mixed line endings: source files written by testCase.write() use
+    // System.lineSeparator(), but echo in the genrule command always produces \n.
+    return invocationOutput.get().replace("\r\n", "\n").replace("\r", "\n");
   }
 
   public final void runNoLossSmokeTest() throws Exception {