process cases of ALT as special rules

src/Nitload.Native/README.md

@@ -6,6 +6,32 @@ Though this project do has a .vcxproj file,
 you can only edit but not compile in visul studio.  
 Currently you can only compile this lib via Clang and cmake.
 
+## Build output and managed deployment
+
+From the repository root:
+
+```powershell
+cmake --preset clang-debug -S src/Nitload.Native
+cmake --build cmake_build/clang-debug --target Nitload.Native
+```
+
+CMake writes `Nitload.Native.dll` and its linker PDB to `bin/win-x64` on Windows x64
+(Linux uses `bin/linux-x64/libNitload.Native.so`). Debug and release presets currently
+share this platform directory; the most recent native build is the deployed version.
+`NIF_BUILD_OUTPUT_DIR` can override the destination. Managed builds pass their expected
+RID as `NIF_EXPECTED_RID` so an incompatible native target is rejected before deployment.
+
+`StgSharpDebug.csproj` enables `BuildNativeBeforeManaged` and `RequireNativeLibrary`.
+Its build runs the incremental CMake build (`clang-debug` for Debug, `clang-release`
+otherwise), then deploys the native library to the executable's actual `TargetDir`.
+Other managed projects copy an existing native artifact without invoking CMake.
+Managed-output staging never copies deployed native files back over the CMake artifact.
+
+To use a prebuilt native artifact, pass `-p:BuildNativeBeforeManaged=false`. A matching
+Clang/Ninja environment and the local GLFW static library are required for native builds.
+Cross-target builds require a matching toolchain/preset; changing a managed platform alone
+does not cross-compile the C library.
+
 ## Code Layout
 
 Conventions: