Write shaderCache.bin next to the executable instead of CWD

[bghgary]

Problem

ShaderCache.SaveAndLoad writes shaderCache.bin to the current working directory:

static const char* shaderCacheFileName = "shaderCache.bin";
std::ofstream stream(shaderCacheFileName, std::ios::binary);

When UnitTests.exe is launched from anywhere that isn't the build output directory (e.g. the repo root), the file lands in that directory and is never cleaned up. A unit test should not leave artifacts in the user's working directory.

Fix

Write the file next to the executable instead. Added a GetExecutableDirectory() helper declared in App.h and implemented per-platform:

• Win32 — GetModuleFileNameW(nullptr, ...)
• Apple — _NSGetExecutablePath + std::filesystem::canonical
• X11/Linux — std::filesystem::canonical("/proc/self/exe")

The test now uses GetExecutableDirectory() / "shaderCache.bin", asserts each stream opened successfully, and asserts on the result of std::filesystem::remove so silent cleanup failures are visible.

No collisions between concurrent runs are possible (each CMake build has its own UnitTests.exe), and artifacts land alongside the build output rather than in the user's current directory or system temp.

Testing

Ran UnitTests.exe --gtest_filter="ShaderCache.*" from the repo root: test passes, no shaderCache.bin left behind at the repo root or next to the executable.

[Created by Copilot on behalf of @bghgary]

[Copilot]

Pull request overview

Updates the ShaderCache unit test to avoid writing shaderCache.bin into the user’s current working directory by moving the artifact to the OS temp directory and attempting to delete it after the round-trip.

Changes:

• Switch shader cache file location from CWD to std::filesystem::temp_directory_path().
• Add a best-effort cleanup via std::filesystem::remove(..., std::error_code&).