build: fix STAGING_DIR cleaning when filenames contain spaces

When looping through a package's STAGING_FILES_LIST (a list of
file/directory paths delimited by newlines), if the path contains
spaces, then the path will be split by the while loops, and the
file/directory will not be deleted/removed.

This sets the internal field separator to the newline only so that the
entire path is considered when deleting/removing.

Signed-off-by: Jeffery To <jeffery.to@gmail.com>

scripts/clean-package.sh

@@ -1,4 +1,5 @@
 #!/usr/bin/env bash
+IFS=$'\n'
 [ -n "$1" -a -n "$2" ] || {
 	echo "Usage: $0 <file> <directory>"
 	exit 1