Output errors on stderr.

platform-darwin/Scripts/updatePlist

@@ -1,7 +1,7 @@
 #!/usr/bin/env bash
 cd "${BASH_SOURCE%/*}"
 source ./bashlib
-trap 'c=$BASH_COMMAND s=$?; (( s )) && echo "ERROR: $s: $c"; exit $s' EXIT
+trap 'c=$BASH_COMMAND s=$?; (( s )) && echo >&2 "ERROR: $s: $c"; exit $s' EXIT
 set -e
 cd ..
 export PATH+=:/usr/libexec