The binary linux SDK in version 17 requires a newer glibc than we have
available, so we have to use our own patched clang. This follows the
approach in:
https://github.com/WebAssembly/wasi-sdk/pull/271
WASI.cmake taken from the wasi-sdk repository.
To address the build time warning:
System is unknown to cmake, create:
Platform/WASI to use this system, please post your config file on
discourse.cmake.org so it can be added to cmake