Make polkit support optional

This commit makes the inclusion of support for PolicyKit optional. It is
enabled by default for compatibility with existing builds, but can be
disabled by passing `--without-polkit` to `rpmbuild`.

spice-gtk.spec

@@ -1,4 +1,5 @@
 #define _version_suffix
+%define with_polkit        0%{!?_without_polkit:1}
 
 Name:           spice-gtk
 Version:        0.34
@@ -23,7 +24,9 @@ BuildRequires: cyrus-sasl-devel
 BuildRequires: libcacard-devel
 BuildRequires: gobject-introspection-devel
 BuildRequires: libacl-devel
+%if %{with_polkit}
 BuildRequires: polkit-devel
+%endif
 BuildRequires: gtk-doc
 BuildRequires: vala-tools
 BuildRequires: usbutils
@@ -110,10 +113,19 @@ find . -name '*.stamp' | xargs touch
 
 
 %build
+%if %{with_polkit}
+    %define usb_acl_helper %{_libexecdir}/spice-gtk-%{_arch}/
+    %define arg_polkit --with-polkit
+    %define arg_usb_acl_helper --with-usb-acl-helper-dir=%{usb_acl_helper}
+%else
+    %define arg_polkit --without-polkit
+%endif
+
 %configure \
     --enable-gtk-doc \
     --enable-webdav \
-    --with-usb-acl-helper-dir=%{_libexecdir}/spice-gtk-%{_arch}/ \
+    %{?arg_polkit} \
+    %{?arg_usb_acl_helper} \
     --enable-lz4 \
     --enable-vala \
     --disable-werror
@@ -150,9 +162,11 @@ rm -f %{buildroot}%{_libdir}/*.la
 %{_libdir}/libspice-client-glib-2.0.so.*
 %{_libdir}/libspice-controller.so.*
 %{_libdir}/girepository-1.0/SpiceClientGLib-2.0.typelib
+%if %{with_polkit}
 %dir %{_libexecdir}/spice-gtk-%{_arch}/
 %attr(4755, root, root) %{_libexecdir}/spice-gtk-%{_arch}/spice-client-glib-usb-acl-helper
 %{_datadir}/polkit-1/actions/org.spice-space.lowlevelusbaccess.policy
+%endif
 
 %files -n spice-glib-devel
 %{_libdir}/libspice-client-glib-2.0.so