Add project files (part 1/2)

Co-Authored-By: Claude Sonnet 5 <[email protected]>

injector/build-windows.sh

@@ -0,0 +1,11 @@
+#!/bin/sh
+# Cross-build slinky-inject.exe with MinGW-w64.
+set -e
+cd "$(dirname "$0")"
+cmake -S . -B build-windows \
+    -DCMAKE_SYSTEM_NAME=Windows \
+    -DCMAKE_C_COMPILER=x86_64-w64-mingw32-gcc \
+    -DCMAKE_CXX_COMPILER=x86_64-w64-mingw32-g++ \
+    -DCMAKE_BUILD_TYPE=Release
+cmake --build build-windows -j"$(nproc)"
+echo "built: $(pwd)/build-windows/slinky-inject.exe"