Provide default arguments for SRCDIR and KEYLIST, so that you can just run this
from the root of the source tree, separately from make distcheck.
# check that all key names in keymaps/* are known in <linux/input.h>
# and that all key maps listed in the rules are valid and present in
# Makefile.am
-SRCDIR=$1
-KEYLIST=$2
+SRCDIR=${1:-.}
+KEYLIST=${2:-extras/keymap/keys.txt}
KEYMAPS_DIR=$SRCDIR/extras/keymap/keymaps #extras/keymap/keymaps
RULES=$SRCDIR/extras/keymap/95-keymap.rules