Add CMake-generated Android APK packaging

[Solessfir]

First part of Android support, limited to APK packaging. Events, Vulkan swapchain handling and controllers are left for separate PRs.

• Generate one build.gradle from CMake, with no root/app split. The application supplies its own manifest.
• Define the native shared library and call add_android_apk(... CODE target ...) in the same CMakeLists.txt. Tempest includes the helper automatically. Gradle builds that same project, with packaging generation disabled in its inner build.
• Use an installed Gradle for command-line builds. No wrapper files, settings.gradle or gradle.properties are included.
• Respect CMake's Android ABI, minimum API, NDK path, STL and native build type settings.
• Support application sources, resources, dependencies and signing, with optional release crash-symbol archives.
• Include a small native packaging example, independent of the Tempest Android backend.
• Leave desktop builds unchanged.

Usage

With JDK 17, Gradle 8.9, the Android SDK, CMake and Ninja configured (replace /path/to/ndk with the NDK installation directory):

cmake -S Examples/Android -B build/android-example -G Ninja -DCMAKE_TOOLCHAIN_FILE=/path/to/ndk/build/cmake/android.toolchain.cmake -DANDROID_ABI=arm64-v8a -DANDROID_PLATFORM=android-24 -DCMAKE_BUILD_TYPE=Release
cmake --build build/android-example --target TempestExample-apk

APK: build/android-example/TempestExample-apk/build/outputs/apk/release/TempestExample-apk-release.apk

A short usage example is in Examples/Android/README.md. Release builds use the local debug signing key unless distribution signing is configured.

Verified Windows command-line Release and Debug ARM64 builds, uncompressed native-library packaging, APK signing and 16 KiB alignment. Also checked custom NDK/API/STL settings and an x86_64 RelWithDebInfo build with a separate full symbol archive. Android Studio import has not been checked locally.

[Try]

Thanks for the PR @Solessfir !

We would have to split it into parts, as-is there are too many separated things to review.

Just some overall notes:

• no need to have multiple build.gradle/settings.gradle files - those can be flatten into a single one
• when list time I've tested gragle*.* files were unneeded. At least when project is opened in AndroidStudio, everything other than build.gradle can be auto-generated. (not sure about command-line)
  probably that part will require some iterations, before merge.

Afterward we can have a look separatly at:

• event system
• swapchain
• controller

[Solessfir]

Yep, makes sense. I'll split it up and start with the packaging part. I'll simplify the Gradle layout and check what's actually needed for both Android Studio and command-line builds. Then we can go through events, swapchain and controllers separately.

[Solessfir]

Done, narrowed this to packaging only and flattened it to a single build.gradle. No settings.gradle, gradle.properties or wrapper files now. Command-line builds use an installed Gradle.

Release and Debug builds work from the command line. The example uses Android's built-in NativeActivity, so it doesn't depend on the Tempest backend changes. I haven't checked Android Studio import locally yet.

Events, swapchain and controllers are kept out of this PR for separate review later.

[Try]

Do you need multi-gig .apk? I've been assuming that gothic-assets will be located somewhere in external-storage folder.

[Try]

do you need it? You already have max-page-size=16384 CMakeLists.txt

[Try]

should we rather about existing cmake variables here?

maybe only set some defaults...

[Solessfir]

• Removed forced repackaging and legacy compression.
• Reused standard CMake Android settings.
• Made symbol archives optional.
• Moved the manifest into the example app.

[Try]

Would it be possible to have one cmake file instead of two?
Ideally, I'm thinking about:

# will be hidden at 'add_subdirectory(Tempest)' level
include(../../Engine/cmake/TempestAndroid.cmake)

and then:

# similar to old Tegra sdk
add_android_apk(target_name package manifest CPP_SOURCE ...)

and in OpenGothic we will add something similar to:

# at very start
if(ANDROID)
  add_library(Gothic2Notr SHARED) # generally same as regular PC build
else()
  add_executable(Gothic2Notr)
endif()
...
# close to the end
if(ANDROID)
  add_android_apk(Gothic2Notr_apk 
          MANIFEST AndroidManifest.xml.in 
          CODE Gothic2Notr
          PACKAGE_NAME "opengothic.gothic2"
      )
endif()

[Try]

We probably don't need this (see comment in Examples/Android/CMakeLists.txt)

[Solessfir]

• One CMake project with add_android_apk(... CODE target ...).
• Helper included automatically by Tempest.
• No recursive packaging generation.
• Shortened README and removed the signing tutorial.

[Try]

There are many small things that I wish to change, but this can wait :)
Looks good to merge, thanks!