[NetworkManager-pptp] build: --without-gnome fix

[Thomas Haller <thaller src gnome org>]

commit 28317b93099106b0e73323e99113e56f0e7240c6
Author: Douglas Kosovic <doug uq edu au>
Date:   Sun Sep 30 12:51:55 2018 +1000

    build: --without-gnome fix
    
    Don't build GNOME based properties if --without-gnome is specified.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=797229
    
    [thaller redhat com: modified original patch for libnm-vpn-plugin-pptp.la]

 Makefile.am | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/Makefile.am b/Makefile.am
index 90fe2be..f3df202 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -175,7 +175,9 @@ properties_libnm_vpn_plugin_pptp_la_LDFLAGS = \
 
 ###############################################################################
 
+if WITH_GNOME
 plugin_LTLIBRARIES += properties/libnm-vpn-plugin-pptp-editor.la
+endif
 
 properties_libnm_vpn_plugin_pptp_editor_la_SOURCES = \
        $(editor_sources)