Simplify flatpak conditionals

There's no need to exclude systemd unit files: instead we can just pass
the directory where they should go and avoid flatpak conditionals.

https://bugzilla.redhat.com/show_bug.cgi?id=1728303

evolution-data-server.spec

@@ -89,9 +89,7 @@ BuildRequires: gtk-doc >= %{gtk_doc_version}
 BuildRequires: intltool >= %{intltool_version}
 BuildRequires: make
 BuildRequires: vala
-%if ! 0%{?flatpak}
 BuildRequires: systemd
-%endif
 
 BuildRequires: pkgconfig(gcr-3)  >= %{gcr_version}
 BuildRequires: pkgconfig(gcr-base-3)  >= %{gcr_version}
@@ -264,9 +262,7 @@ export CFLAGS="$RPM_OPT_FLAGS -DLDAP_DEPRECATED -fPIC -I%{_includedir}/et -Wno-d
 	-DENABLE_INTROSPECTION=ON \
 	-DENABLE_VALA_BINDINGS=ON \
 	-DENABLE_INSTALLED_TESTS=ON \
-        %if 0%{?flatpak}
+        -DWITH_SYSTEMDUSERUNITDIR=%{_userunitdir} \
-        -DWITH_SYSTEMDUSERUNITDIR=OFF \
-        %endif
 	%if "%{?_eds_dbus_services_prefix}" != ""
 	-DDBUS_SERVICES_PREFIX=%{?_eds_dbus_services_prefix} \
 	%endif
@@ -356,12 +352,10 @@ find $RPM_BUILD_ROOT -name '*.so.*' -exec chmod +x {} \;
 %{_datadir}/dbus-1/services/%{dbus_service_name_user_prompter}.service
 %{_datadir}/pixmaps/evolution-data-server
 
-%if ! 0%{?flatpak}
 %{_userunitdir}/evolution-addressbook-factory.service
 %{_userunitdir}/evolution-calendar-factory.service
 %{_userunitdir}/evolution-source-registry.service
 %{_userunitdir}/evolution-user-prompter.service
-%endif
 
 %dir %{_libdir}/evolution-data-server
 %dir %{credential_modules_dir}