[tools] Make tick processor report error to stderr.

R=herhut@chromium.org

Change-Id: Iaac8c2e036a0343c4d4a5c50bc91fb3d35e5d760
Reviewed-on: https://chromium-review.googlesource.com/c/1319586Reviewed-by: Stephan Herhut <herhut@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57282}

tools/linux-tick-processor

@@ -27,8 +27,8 @@ if [ ! -x "$d8_exec" ]; then
 fi
 
 if [ ! -x "$d8_exec" ]; then
-  echo "d8 shell not found in $D8_PATH"
-  echo "Please provide path to d8 as env var in D8_PATH"
+  echo "d8 shell not found in $D8_PATH" >&2
+  echo "Please provide path to d8 as env var in D8_PATH" >&2
   exit 1
 fi