Avoid to fail on killall without any argiments in case of libselinux

--- configure.ac
+++ configure.ac	2021-01-14 12:52:33.493812041 +0100
@@ -27,6 +27,8 @@ if test "$enable_selinux" = "yes"; then
   AC_DEFINE([WITH_SELINUX], [1], [Use Security-Enhanced Linux features])
   AC_CHECK_LIB([selinux], [getfilecon], [SELINUX_LIB=-lselinux], [
      AC_MSG_ERROR([Cannot find selinux static library]) ])
+  AC_CHECK_LIB([selinux], [getfilecon], [echo 'set has_selinux 1' > testsuite/selinux.exp],
+     [echo 'set has_selinux 0' > testsuite/selinux.exp])
 fi
 AC_SUBST([SELINUX_LIB])
 
--- testsuite/Makefile.am
+++ testsuite/Makefile.am	2021-01-14 12:53:25.962505766 +0100
@@ -1,6 +1,8 @@
 AUTOMAKE_OPTIONS = dejagnu
 export DEJAGNU
 
+EXTRA_DEJAGNU_SITE_CONFIG=$(srcdir)/selinux.exp
+
 # Programs that are expected across the board.
 DEJATOOL = killall
 DEJATOOL += pslog
--- testsuite/killall.test/killall.exp
+++ testsuite/killall.test/killall.exp	2021-01-14 12:54:27.087313939 +0100
@@ -7,7 +7,11 @@ set fake_proc_name "afakeprocname"
 
 set test "killall with no arguments"
 spawn $killall
+if { $has_selinux == 0 } {
 expect_pass "$test" "^Usage: killall \\\[OPTION\\\]\\.\\.\\. \\\[--\\\] NAME\\.\\.\\."
+} else {
+expect_pass "$test" "^Usage: killall \\\[ -Z CONTEXT \\\] \\\[ -u USER \\\] \\\[ -y TIME \\\] \\\[ -o TIME \\\] \\\[ -eIgiqrvw \\\]"
+}
 
 set test "killall list signals"
 spawn $killall -l