[Enaium]

Summary

Adds a windowsarm64 native build target to generateLibs, using gdx-jnigen's Windows ARM64 target and the LLVM-MinGW aarch64-w64-mingw32-* wrappers. The x86_64 Windows path is refactored into a shared createWindowsTarget() helper and keeps its current output filename.

Also:

• applies a vendor patch adding <exception> to imgui-node-editor's crude_json.cpp, required by the libc++ used by LLVM-MinGW;
• adds LWJGL natives-windows-arm64 classifiers to imgui-app;
• documents the direct Gradle build path for Windows ARM64.

Type of change

• New feature (non-breaking change which adds functionality)

Notes for reviewer

• Tested on Windows 11 ARM64 (Apple Silicon VM): generateLibs -Denvs=windowsarm64 -Dlocal succeeds; output windowsarm64/imgui-java64.dll has PE machine 0xAA64. The existing windows64 target still builds (0x8664).
• JNI smoke on the ARM64 DLL produced a font atlas and draw data successfully. On a combined test branch with the SDL_Renderer backend, the example rendered through SDL's software renderer (no GPU): 640x360 readback with the expected text pixels.
• imgui-app now carries ARM64 LWJGL natives, but bin/ and the published app jar still contain only the x64 ImGui DLL; shipping/bundling the ARM64 DLL is left to the release/CI path.
• buildSrc/scripts/build.sh windowsarm64 / FreeType vendoring is not wired: a FreeType Windows ARM64 build needs a native autotools environment. The documented direct Gradle path builds without FreeType, like the other direct paths.