'webkitgtk-3.0' not found in specified Vala API

[ 56%] Built target geary-engine
[ 56%] Generating .geary-client.stamp
error: GResources file `/home/ralph/git/geary/build/ui/.gresource.xml' does not exist
/home/ralph/git/geary/src/client/components/empty-placeholder.vala:12.1-12.40: error: UI resource not found: `/org/gnome/Geary/empty-placeholder.ui'. Please make sure to specify the proper GResources xml files with --gresources.
public class EmptyPlaceholder : Gtk.Grid {
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
/home/ralph/git/geary/src/client/components/folder-popover.vala:8.1-8.40: error: UI resource not found: `/org/gnome/Geary/folder-popover.ui'. Please make sure to specify the proper GResources xml files with --gresources.
public class FolderPopover : Gtk.Popover {
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
/home/ralph/git/geary/src/client/components/main-toolbar.vala:9.1-9.34: error: UI resource not found: `/org/gnome/Geary/main-toolbar.ui'. Please make sure to specify the proper GResources xml files with --gresources.
public class MainToolbar : Gtk.Box {
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
/home/ralph/git/geary/src/client/components/main-window.vala:10.1-10.47: error: UI resource not found: `/org/gnome/Geary/main-window.ui'. Please make sure to specify the proper GResources xml files with --gresources.
public class MainWindow : Gtk.ApplicationWindow {
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
/home/ralph/git/geary/src/client/composer/composer-headerbar.vala:8.1-8.46: error: UI resource not found: `/org/gnome/Geary/composer-headerbar.ui'. Please make sure to specify the proper GResources xml files with --gresources.
public class ComposerHeaderbar : Gtk.HeaderBar {
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
/home/ralph/git/geary/src/client/composer/composer-widget.vala:14.1-14.42: error: UI resource not found: `/org/gnome/Geary/composer-widget.ui'. Please make sure to specify the proper GResources xml files with --gresources.
public class ComposerWidget : Gtk.EventBox {
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
/home/ralph/git/geary/src/client/conversation-viewer/conversation-email.vala:19.1-19.40: error: UI resource not found: `/org/gnome/Geary/conversation-email.ui'. Please make sure to specify the proper GResources xml files with --gresources.
public class ConversationEmail : Gtk.Box {
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
/home/ralph/git/geary/src/client/conversation-viewer/conversation-email.vala:94.5-94.43: error: UI resource not found: `/org/gnome/Geary/conversation-email-attachment-view.ui'. Please make sure to specify the proper GResources xml files with --gresources.
    private class AttachmentView : Gtk.Grid {
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
/home/ralph/git/geary/src/client/conversation-viewer/conversation-message.vala:18.1-18.43: error: UI resource not found: `/org/gnome/Geary/conversation-message.ui'. Please make sure to specify the proper GResources xml files with --gresources.
public class ConversationMessage : Gtk.Grid {
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
/home/ralph/git/geary/src/client/conversation-viewer/conversation-viewer.vala:13.1-13.43: error: UI resource not found: `/org/gnome/Geary/conversation-viewer.ui'. Please make sure to specify the proper GResources xml files with --gresources.
public class ConversationViewer : Gtk.Stack {
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Compilation failed: 11 error(s), 0 warning(s)
make[2]: *** [src/CMakeFiles/geary-client.dir/build.make:402: src/.geary-client.stamp] Fehler 1
make[1]: *** [CMakeFiles/Makefile2:846: src/CMakeFiles/geary-client.dir/all] Fehler 2
make: *** [Makefile:128: all] Fehler 2
[ralph@six build]$