+# List module undefined symbols
+ifdef CONFIG_TRIM_UNUSED_EXPSYMS
+cmd_undef_syms = $(NM) $@ | sed -n 's/^ \+U \(.*\)/\1/p' | xargs echo
+else
+cmd_undef_syms = echo
+endif

Use ":" as a "do nothing" cammand. Then you do not emit an empty line.

	Sam