[OpenXR] Use includes from Maven package (#1552)

We've recently improved our build process by getting the OpenXR
library from Maven. That allowed us to, among other things,
use the already compiled khronos loader instead of the propietary
ones.

However we could do even better by also using the maven package
even for those configurations that require a propietary loader.
In this case we would use it to get the OpenXR include files.

This will allow us to remove the OpenXR-SDK submodule from the
third parties repo as it won't be no longer needed.

README.md

@@ -47,7 +47,6 @@ This repo is only available to Igalia members. If you have access to the relevan
  - `third_party/wavesdk/` for Vive (should contain a `build` folder, among other things)
  - `third_party/picoxr` [Pico OpenXR Mobile SDK](https://developer-global.pico-interactive.com/sdk?deviceId=1&platformId=3&itemId=11) (should contain `libs` folders, among other things that are not necessary for Wolvic)
  - `third_party/spaces` [for Snapdragon Spaces](https://spaces.qualcomm.com/)(should contain `libopenxr_loader.aar`)
- - `third_party/OpenXR-SDK/` [OpenXR-SDK](https://github.com/KhronosGroup/OpenXR-SDK) (should contain an `include` folder). This is used by HVR and PicoXR flavours. The other flavours using OpenXR use the include files provided by the Khronos OpenXR loader AAR from Maven.
  - `third_party/aliceimu/` for [Huawei Vision Glass](https://consumer.huawei.com/cn/wearables/vision-glass/) (should contain an `.aar` file with the IMU library for the glasses)
 
 The [repo in `third_party`](https://github.com/Igalia/wolvic-third-parties) can be updated like so:

app/CMakeLists.txt

@@ -96,16 +96,15 @@ endif()
 if(OPENXR)
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DXR_USE_PLATFORM_ANDROID -DXR_USE_GRAPHICS_API_OPENGL_ES")
     find_package(OpenXR REQUIRED CONFIG)
+    target_link_libraries(native-lib PRIVATE OpenXR::headers)
     include_directories(${CMAKE_SOURCE_DIR}/../app/src/openxr/cpp)
     if (HVR)
-        include_directories(${CMAKE_SOURCE_DIR}/../third_party/OpenXR-SDK/include)
         add_custom_command(TARGET native-lib POST_BUILD
                 COMMAND ${CMAKE_COMMAND} -E copy
                 ${CMAKE_SOURCE_DIR}/../third_party/hvr/${ANDROID_ABI}/libxr_loader.so
                 ${CMAKE_LIBRARY_OUTPUT_DIRECTORY}/libxr_loader.so
                 )
     elseif (PICOXR)
-        include_directories(${CMAKE_SOURCE_DIR}/../third_party/OpenXR-SDK/include)
         add_custom_command(TARGET native-lib POST_BUILD
             COMMAND ${CMAKE_COMMAND} -E copy
             ${CMAKE_SOURCE_DIR}/../third_party/picoxr/libs/android.${ANDROID_ABI}/libopenxr_loader.so

third_party_hash

@@ -1 +1 @@
-59b25b09e0084897dd81675d14e9f47177d52359
+7da99cb21263d74d5bf3d56d210ee85fdbd6d57e