Default to enable driver modules for libvirtd

Always enable driver modules for libvirtd, if we have dlopen
available. This allows more modular packaging by distros
and ensures we don't break this config

* configure.ac: Default to enable driver modules
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

configure.ac

@@ -2422,14 +2422,27 @@ dnl Driver-Modules library
 AC_ARG_WITH([driver-modules],
   AC_HELP_STRING([--with-driver-modules], [build drivers as loadable modules @<:@default=no@:>@]),
   [],
-  [with_driver_modules=no])
+  [with_driver_modules=check])
+
+if test "$with_libvirtd" = "no" ; then
+  with_driver_modules=no
+fi
 
 DRIVER_MODULE_CFLAGS=
 DRIVER_MODULE_LIBS=
-if test "$with_driver_modules" = "yes"; then
+if test "$with_driver_modules" = "yes" || test "$with_driver_modules" = "check"; then
   if test "$dlfcn_found" != "yes" || test "$dlopen_found" != "yes"; then
-    AC_MSG_ERROR([You must have dlfcn.h / dlopen() support to build driver modules])
+    if test "$with_driver_modules" = "yes" ; then
+      AC_MSG_ERROR([You must have dlfcn.h / dlopen() support to build driver modules])
+    else
+      with_driver_modules=no
+    fi
+  else
+    with_driver_modules=yes
   fi
+fi
+
+if test "$with_driver_modules" = "yes" ; then
   DRIVER_MODULE_CFLAGS="-export-dynamic"
   case $ac_cv_search_dlopen in
     no*) DRIVER_MODULE_LIBS= ;;