Write cross-platform builds

Produce cross-platform builds for Windows, macOS, and Linux from our single codebase. Write CMake rules that produce a debug and release target for each platform, use toolchain files for macOS and Windows compilers, ensure resource files are packaged correctly on macOS bundles and Windows installer, and add CI jobs that run unit tests on all three platforms on every merge.

Before I commit the new build scripts, make them easy for the release engineer to review. Surface where platform-specific code lives, document compiler flags that affect ABI or floating-point behavior, show how to generate signed macOS bundles and Windows installers locally, and flag any third-party libs that need separate builds per platform.

I added platform-specific code and set up CMake toolchain files; CI shows Linux and macOS executables build, but the Windows job fails with unresolved externals referencing our logging symbols. I suspect name-mangling or missing linkage with the logging static lib. I cannot reproduce a Windows dev environment locally easily. What are the likely causes and the quickest steps to identify and fix the missing symbols on Windows CI?

We repeatedly ship bugs caused by differences between platform builds: alignment, calling conventions, and missing linker flags. Each release I spend cycles chasing platform regressions that passed on Linux. What process or build policy should I adopt so platform divergence is detected and controlled earlier, reducing last-minute platform-specific fixes?