Address config/build warnings for Cardboard SDK with NDK v27.X

[tellypresence]

When building Cardboard SDK with Android Studio Koala Feature Drop Patch 1 and NDK v27.X (supported since Cardboard v1.26.0) several warnings are reported. It would be good to address the root causes in an effort to make the build warning-free.

SDK XML version 4 was encountered warning

> Task :sdk:sdk:configureCMakeDebug[arm64-v8a]
[CXX5304] This version only understands SDK XML versions up to 3 but an SDK XML file of version 4 was encountered. 
This can happen if you use versions of Android Studio and the command-line tools that were released at different times.

Missing project() command in CMakeLists.txt:

C/C++: CMake Warning (dev) in CMakeLists.txt:
C/C++:   No project() command is present.  The top-level CMakeLists.txt file must
C/C++:   contain a literal, direct call to the project() command.  Add a line of
C/C++:   code such as
C/C++:     project(ProjectName)
C/C++:   near the top of the file, but after cmake_minimum_required().
C/C++:   CMake is pretending there is a "project(Project)" command on the first
C/C++:   line.
C/C++: This warning is for project developers.  Use -Wno-dev to suppress it.

Missing field initializer warnings in 3 source files:

<...>/cardboard/sdk/rendering/android/vulkan_distortion_renderer.cc
<...>/cardboard/sdk/unity/xr_unity_plugin/vulkan/vulkan_renderer.cc
<...>/cardboard/sdk/unity/xr_unity_plugin/vulkan/vulkan_widgets_renderer.cc

e.g.

C/C++: <...>/cardboard/sdk/rendering/android/vulkan_distortion_renderer.cc:190:49: warning: 
    missing field 'pNext' initializer [-Wmissing-field-initializers]
C/C++: 15 warnings generated.

Also in vulkan_renderer.cc
C/C++: <...>/cardboard/sdk/unity/xr_unity_plugin/vulkan/vulkan_renderer.cc:308:5: warning: 
    missing field 'flags' initializer [-Wmissing-field-initializers]
C/C++: 10 warnings generated.

C/C++: <...>/cardboard/sdk/unity/xr_unity_plugin/vulkan/vulkan_widgets_renderer.cc:134:74: warning: 
    missing field 'pNext' initializer [-Wmissing-field-initializers]
C/C++: 14 warnings generated.

invalid ABI 'riscv64' configuration warning

There's also this warning; not sure if it's Cardboard-specific or due to NDK v27.X

WARNING: C/C++: Ignoring invalid ABI 'riscv64' found in ABI metadata file 
    '<...>/Android/Sdk/ndk/27.1.12297006/meta/abis.json'.
C/C++: Ignoring invalid ABI 'riscv64' found in ABI metadata file '<...>/Android/Sdk/ndk/27.1.12297006/meta/abis.json'.