Don't leak file descriptors

We're leaking file descriptors to child processes. Set FD_CLOEXEC on file
descriptors that don't need to be passed to children to stop this misbehaviour.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/configure b/configure
index 8b8b94c..ef15948 100755
--- a/configure
+++ b/configure
@@ -1570,6 +1570,23 @@
   pipe2=yes
 fi
 
+# check if accept4 is there
+accept4=no
+cat > $TMPC << EOF
+#define _GNU_SOURCE
+#include <sys/socket.h>
+#include <stddef.h>
+
+int main(void)
+{
+    accept4(0, NULL, NULL, SOCK_CLOEXEC);
+    return 0;
+}
+EOF
+if compile_prog "" "" ; then
+  accept4=yes
+fi
+
 # check if tee/splice is there. vmsplice was added same time.
 splice=no
 cat > $TMPC << EOF
@@ -2014,6 +2031,9 @@
 if test "$pipe2" = "yes" ; then
   echo "CONFIG_PIPE2=y" >> $config_host_mak
 fi
+if test "$accept4" = "yes" ; then
+  echo "CONFIG_ACCEPT4=y" >> $config_host_mak
+fi
 if test "$splice" = "yes" ; then
   echo "CONFIG_SPLICE=y" >> $config_host_mak
 fi