Delete all .pyc on update. Stale .pyc can cause weird issues.

Take two at r102841.

Forgot to use $base_dir, so the .pyc files in the checkout were deleted, instead
of the ones in depot_tools. Since some slaves have very large checkouts, they
appeared as hung.

R=cmp@chromium.org
BUG=
TEST=


Review URL: http://codereview.chromium.org/8059001

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@103056 0039d316-1c4b-4281-b951-d872f2087c98

update_depot_tools

@@ -94,3 +94,5 @@ then
     echo "Depot Tools has been updated to revision $AFTER_REVISION." 1>&2
   fi
 fi
+
+find "$base_dir" -iname "*.pyc" -delete