fix fetch on aix

The `find` utility does not support iname option. Use grep to work
around this limitation.

Change-Id: Iee16def0e4eea8b868c4f3aad164caa0bd7e9d5d
Reviewed-on: https://chromium-review.googlesource.com/1106651
Commit-Queue: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>

update_depot_tools

@@ -123,6 +123,6 @@ if [ "X$DEPOT_TOOLS_UPDATE" != "X0" ]; then
   source "$base_dir/cipd_bin_setup.sh"
   cipd_bin_setup
 
-  find "$base_dir" -iname "*.pyc" -exec rm -f {} \;
+  find "$base_dir" | grep -i ".*\.pyc" | xargs rm -f;
 fi