Linux executables (apphosts) are needed by the build now that we use them by default since #80026. However, the officially published toolset package is built on Windows and currently contains only Windows apphosts (e.g., csc.exe). Hence using the toolset package on Linux is broken (cannot find csc).
The toolset package is also used to transport the compiler into the SDK, hence the compiler layout is incomplete on non-Windows platforms.