kiss-size: fix bug when kiss-size runs on big packages

Previously, if kiss-size was ran on a package that owns a lot of
files, kiss-size would error out. This is because du wasn't
able to handle the number of files provided to it.

This patch solves this issue, by avoiding the generation of the 'files'
variable, and instead piping directly into xargs which then feeds the
files to du.

For an example package that breaks with the previous implementation,
see https://github.com/ehawkvu/kiss-tex/tree/master/texlive/texlive-fontsextra
which installs around 94,000 files.

contrib/kiss-size

@@ -27,14 +27,11 @@ kiss list "${1:-null}" >/dev/null || {
 
 # Filter directories from manifest and leave only files.
 # Directories in the manifest end in a trailing '/'.
-files=$(sed -e "s|^|$KISS_ROOT|" -e 's|.*/$||' \
-    "$KISS_ROOT/var/db/kiss/installed/$1/manifest")
-
-# Send the file list to 'du'.
-# This unquoted variable is safe as word splitting is intended
-# and globbing is globally disabled in this script.
-# shellcheck disable=2086
-du -sk -- $files 2>/dev/null |
+# Send the file list to 'xargs' to run through 'du',
+# this prevents du from exiting due to too many arguments
+sed -e "s|^|$KISS_ROOT|" -e 's|.*/$||' \
+    "$KISS_ROOT/var/db/kiss/installed/$1/manifest" \
+    | xargs du -sk -- 2>/dev/null |
 
 # Iterate over each line and convert the byte output to human
 # readable (MB, KB, GB, etc).