Subzero: Fix a warning message in the browser build.

Due to a mistake in the logic in https://codereview.chromium.org/1903553004 , a warning is printed even when LogFilename is properly set to "-".

BUG= https://bugs.chromium.org/p/nativeclient/issues/detail?id=4370
R=jpp@chromium.org

Review URL: https://codereview.chromium.org/1911713002 .
diff --git a/src/IceBrowserCompileServer.cpp b/src/IceBrowserCompileServer.cpp
index 0b622df..8b94a97 100644
--- a/src/IceBrowserCompileServer.cpp
+++ b/src/IceBrowserCompileServer.cpp
@@ -277,7 +277,9 @@
   InputStream = new llvm::QueueStreamer();
   bool LogStreamFailure = false;
   int LogFD = STDOUT_FILENO;
-  if (getFlags().getLogFilename() == "/dev/stderr") {
+  if (getFlags().getLogFilename() == "-") {
+    // Common case, do nothing.
+  } else if (getFlags().getLogFilename() == "/dev/stderr") {
     LogFD = STDERR_FILENO;
   } else {
     LogStreamFailure = true;