Add POSIX compat headers and bundle 7za.exe for MSVC

Fix Dockerfile CMD args broken by triplet rename

Update README and build.sh args to match renamed triplets

Rename triplets: x64-linux-generic→x64-linux, x64-mingw-static→x64-mingw

Build SDL2 as a DLL on MinGW (matches Linux and MSVC behaviour)

Update README to reflect post-initial-commit changes

CI: test vcpkg binary cache hit after pinning

Pin vcpkg to builtin-baseline commit and fix binary cache key

Add native MSVC Windows build target (x64-windows-msvc)

Link freetype and fontconfig statically to minimize external dynamic libs deps (on Linux)

SDL2 should link dynamically actually (on Linux)

png/jpeg fixup pt.1

Initial commit