Make seccomp optional

Several architectures does not have seccomp yet.

configure.ac

@@ -59,9 +59,6 @@ AC_SUBST(BASE_LIBS)
 PKG_CHECK_MODULES(SOUP, [libsoup-2.4])
 AC_SUBST(SOUP_CFLAGS)
 AC_SUBST(SOUP_LIBS)
-PKG_CHECK_MODULES(LIBSECCOMP, [libseccomp])
-AC_SUBST(LIBSECCOMP_CFLAGS)
-AC_SUBST(LIBSECCOMP_LIBS)
 PKG_CHECK_MODULES(OSTREE, [libgsystem >= 2015.1 ostree-1 >= 2015.3])
 AC_SUBST(OSTREE_CFLAGS)
 AC_SUBST(OSTREE_LIBS)
@@ -69,6 +66,21 @@ PKG_CHECK_MODULES(FUSE, [fuse])
 AC_SUBST(FUSE_CFLAGS)
 AC_SUBST(FUSE_LIBS)
 
+AC_ARG_ENABLE([seccomp],
+              AC_HELP_STRING([--disable-seccomp],
+                             [Disable seccomp]),
+              [],
+              [enable_seccomp=yes])
+
+if test "x$enable_seccomp" = "xyes"; then
+   PKG_CHECK_MODULES(LIBSECCOMP, [libseccomp])
+   AC_SUBST(LIBSECCOMP_CFLAGS)
+   AC_SUBST(LIBSECCOMP_LIBS)
+   AC_DEFINE([ENABLE_SECCOMP], [1],
+      [Define if using seccomp])
+fi
+
+
 AC_ARG_ENABLE([userns],
               AC_HELP_STRING([--disable-userns],
                              [Disable User namespaces (requires setuid/setcaps)]),

lib/xdg-app-helper.c

@@ -49,7 +49,9 @@
 #include <sys/utsname.h>
 #include <unistd.h>
 
+#ifdef ENABLE_SECCOMP
 #include <seccomp.h>
+#endif
 
 #if 0
 #define __debug__(x) printf x
@@ -293,6 +295,7 @@ static inline int raw_clone(unsigned long flags, void *child_stack) {
 static void
 setup_seccomp (bool devel)
 {
+#ifdef ENABLE_SECCOMP
   scmp_filter_ctx seccomp;
   /**** BEGIN NOTE ON CODE SHARING
    *
@@ -454,6 +457,7 @@ setup_seccomp (bool devel)
     die_with_error ("Failed to install seccomp audit filter: ");
 
   seccomp_release (seccomp);
+#endif
 }
 
 static void