build: use subdir-objects and CC_C_O

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>

diff --git a/configure.ac b/configure.ac
index 99129eab9df26f3922a503d3f1f230e455d8a0f8..b86ec14dc2a318750909ca05c6708044e9275a96 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -3,7 +3,7 @@ AC_INIT([ipset], [5.0], [kadlec@blackhole.kfki.hu])
 AC_CANONICAL_SYSTEM
 AC_CONFIG_MACRO_DIR([m4])
 AC_CONFIG_HEADER([config.h])
-AM_INIT_AUTOMAKE([-Wall -Werror foreign])
+AM_INIT_AUTOMAKE([-Wall -Werror foreign subdir-objects])
 
 dnl Shortcut: Linux supported alone
 case $target in
@@ -104,6 +104,7 @@ AM_CONDITIONAL([DISABLE_EXTRA_FLAGS], [test "x$extra_flags" = xno])
 
 dnl Checks for programs
 AC_PROG_CC
+AM_PROG_CC_C_O
 AC_PROG_LIBTOOL
 AC_PROG_INSTALL
 AC_PROG_LN_S