Fix RemoteSpawnStrategy to upload stdout/stderr to the remote cache

This is already fixed in the CachedLocalSpawnRunner, with tests there, which
will replace RemoteSpawnStrategy in the near future. For now, I'd like to get
this in in time for 0.5.0 to get test caching working.

Fixes #1413.

PiperOrigin-RevId: 153486592

src/main/java/com/google/devtools/build/lib/remote/RemoteSpawnStrategy.java

@@ -152,6 +152,15 @@ private void execLocally(
       try {
         ActionResult.Builder result = ActionResult.newBuilder();
         actionCache.uploadAllResults(execRoot, outputFiles, result);
+        FileOutErr outErr = actionExecutionContext.getFileOutErr();
+        if (outErr.getErrorPath().exists()) {
+          ContentDigest stderr = actionCache.uploadFileContents(outErr.getErrorPath());
+          result.setStderrDigest(stderr);
+        }
+        if (outErr.getOutputPath().exists()) {
+          ContentDigest stdout = actionCache.uploadFileContents(outErr.getOutputPath());
+          result.setStdoutDigest(stdout);
+        }
         actionCache.setCachedActionResult(actionKey, result.build());
         // Handle all cache errors here.
       } catch (IOException e) {