cmake: fix custom openxr target builds

MR.2401 made a change where the state_tracker directory
is now conditionally recursed into only if the main
openxr feature is enabled, this breaks derived runtimes
which have custom openxr/serivce/service-lib targets
that depend on the oxr target.

Part-of: <https://gitlab.freedesktop.org/monado/monado/-/merge_requests/2422>

CMakeLists.txt

···
 option(XRT_MODULE_MONADO_CLI "Build monado-cli" ON)
 option_with_deps(XRT_MODULE_MONADO_GUI "Build monado-gui" DEPENDS XRT_HAVE_SDL2)
 option(XRT_MODULE_AUX_VIVE "Build aux_vive" ON)
+option(XRT_MODULE_OPENXR_STATE_TRACKER "Build OpenXR State Tracker" ON)
 
 # Feature configuration (sorted)
 option_with_deps(XRT_FEATURE_AHARDWARE_BUFFER "Enable AHardwareBuffer for XrSwapchain images on Android (API-level 26+) platforms" DEPENDS ANDROID)
 option_with_deps(XRT_FEATURE_COLOR_LOG "Enable logging in color on supported platforms" DEPENDS XRT_HAVE_LINUX)
-option_with_deps(XRT_FEATURE_OPENXR "Build OpenXR runtime target" DEPENDS "XRT_MODULE_COMPOSITOR_MAIN OR XRT_MODULE_COMPOSITOR_NULL")
+option_with_deps(XRT_FEATURE_OPENXR "Build OpenXR runtime target" DEPENDS XRT_MODULE_OPENXR_STATE_TRACKER "XRT_MODULE_COMPOSITOR_MAIN OR XRT_MODULE_COMPOSITOR_NULL")
 set(XRT_FEATURE_OPENXR_DEBUG_UTILS OFF) # Has never been enabled
 option_with_deps(XRT_FEATURE_RENDERDOC "Enable RenderDoc API" DEPENDS "RT_LIBRARY OR WIN32 OR ANDROID")
 option_with_deps(XRT_FEATURE_SERVICE "Enable separate service module for OpenXR runtime" DEPENDS XRT_MODULE_IPC XRT_FEATURE_OPENXR)
···
 message(STATUS "#    MODULE_IPC:                  ${XRT_MODULE_IPC}")
 message(STATUS "#    MODULE_MONADO_GUI:           ${XRT_MODULE_MONADO_GUI}")
 message(STATUS "#    MODULE_MONADO_CLI:           ${XRT_MODULE_MONADO_CLI}")
+message(STATUS "#    MODULE_OPENXR_STATE_TRACKER: ${XRT_MODULE_OPENXR_STATE_TRACKER}")
 message(STATUS "#")
 message(STATUS "#    FEATURE_AHARDWARE_BUFFER:                      ${XRT_FEATURE_AHARDWARE_BUFFER}")
 message(STATUS "#    FEATURE_CLIENT_DEBUG_GUI:                      ${XRT_FEATURE_CLIENT_DEBUG_GUI}")

src/xrt/state_trackers/CMakeLists.txt

···
 	add_subdirectory(gui)
 endif()
 
-if(XRT_FEATURE_OPENXR)
+if(XRT_MODULE_OPENXR_STATE_TRACKER)
 	add_subdirectory(oxr)
 endif()
 

src/xrt/state_trackers/oxr/CMakeLists.txt

···
 
 if(XRT_HAVE_VULKAN)
 	target_sources(st_oxr PRIVATE oxr_session_gfx_vk.c oxr_swapchain_vk.c oxr_vulkan.c)
-	target_link_libraries(st_oxr PUBLIC Vulkan::Vulkan)
+	target_link_libraries(st_oxr PUBLIC aux_vk)
 endif()
 
 if(XRT_HAVE_OPENGL OR XRT_HAVE_OPENGLES)