Lexer is never run so don't bother

--- a/configure
+++ b/configure
@@ -7131,10 +7131,6 @@
 rm -f conftest.l $LEX_OUTPUT_ROOT.c
 
 fi
-if test "x$LEX" != xflex
-then :
-  as_fn_error $? "kbd depends on flex features, but found '$LEX'." "$LINENO" 5
-fi
 
 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether C compiler accepts -std=gnu11" >&5
 printf %s "checking whether C compiler accepts -std=gnu11... " >&6; }