IWYU: recommend gn_check_autofix.py (and make it executable)

BUG=webrtc:42226242

Change-Id: Ibb34815c4b8f61f7e5f1acb34c456903890f54d9
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/378940
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#44000}
diff --git a/tools_webrtc/gn_check_autofix.py b/tools_webrtc/gn_check_autofix.py
old mode 100644
new mode 100755
diff --git a/tools_webrtc/iwyu/apply-include-cleaner b/tools_webrtc/iwyu/apply-include-cleaner
index 262b601..6967bf4 100755
--- a/tools_webrtc/iwyu/apply-include-cleaner
+++ b/tools_webrtc/iwyu/apply-include-cleaner
@@ -136,8 +136,8 @@
   HAS_OUTPUT=$HAS_OUTPUT || [[ ! -z $OUTPUT ]]
 done
 
-echo "Finished. Check diff, compile, gn gen --check and git cl format"
-echo "before uploading."
+echo "Finished. Check diff, compile, gn gen --check (tools_webrtc/gn_check_autofix.py can fix most of the issues)"
+echo "and git cl format before uploading."
 
 # Return a non-zero exit code if running with "CHECK_MODE"
 # and there are changes to apply.