link seccomp only with softmmu targets

Now, if seccomp is detected, it is linked into every executable,
but is used only by softmmu targets (from vl.c).  So link it
only where it is actually needed.

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
diff --git a/configure b/configure
index c6172ef..b7635e4 100755
--- a/configure
+++ b/configure
@@ -1434,7 +1434,7 @@
 
 if test "$seccomp" != "no" ; then
     if $pkg_config --atleast-version=1.0.0 libseccomp --modversion >/dev/null 2>&1; then
-        LIBS=`$pkg_config --libs libseccomp`
+        libs_softmmu="$libs_softmmu `$pkg_config --libs libseccomp`"
 	seccomp="yes"
     else
 	if test "$seccomp" = "yes"; then