/claim #535

Summary

This PR fixes Windows CMake configuration failures without refactoring or changing runtime logic.

What was broken on Windows

• PreLoad.cmake tried to call uname, which is not available on Windows.
• CMake arch detection treated AMD64 as unsupported.
• The “polluted environment flags” check always failed on Windows because MSVC sets default flags.

Fix (minimal scope)

• Avoid calling uname on Windows; use CMAKE_SYSTEM_NAME and CMAKE_SYSTEM_PROCESSOR.
• Treat AMD64 as x86_64 in CMake arch detection.
• Skip the polluted-env fatal check on WIN32 (MSVC defaults would otherwise abort configure).

Build / Repro (WSL recommended)

git submodule sync --recursive
git submodule update --init --recursive
cmake -S . -B build -G Ninja
ninja -C build -j2

Note: `test_unit_tests_dbms` is long-running on my WSL setup. With `ctest --timeout 900` it times out after ~15 minutes while still making progress (log ends mid-suite, e.g. `StreamingHashJoin.SimpleJoinTests`, not a crash).
Previously on the same setup it completed in ~33 minutes with 11264/11265 passed and 1 failing gtest (`TimeWheel.Concurrency_Thread`).