makepkg: update help text to describe --packagelist's new behavior

In commit d8591dd3

 when teaching
--packagelist to print the full filepath for built arches only, I forgot
to update the helptext at the same time as I updated the manpage.
Signed-off-by: Eli Schwartz <eschwartz@archlinux.org>
Signed-off-by: Allan McRae <allan@archlinux.org>

scripts/makepkg.sh.in

@@ -1180,7 +1180,7 @@ usage() {
 	printf -- "$(gettext "  --nocheck        Do not run the %s function in the %s")\n" "check()" "$BUILDSCRIPT"
 	printf -- "$(gettext "  --noprepare      Do not run the %s function in the %s")\n" "prepare()" "$BUILDSCRIPT"
 	printf -- "$(gettext "  --nosign         Do not create a signature for the package")\n"
-	printf -- "$(gettext "  --packagelist    Only list packages that would be produced, without PKGEXT")\n"
+	printf -- "$(gettext "  --packagelist    Only list package filepaths that would be produced")\n"
 	printf -- "$(gettext "  --printsrcinfo   Print the generated SRCINFO and exit")\n"
 	printf -- "$(gettext "  --sign           Sign the resulting package with %s")\n" "gpg"
 	printf -- "$(gettext "  --skipchecksums  Do not verify checksums of the source files")\n"