web-wasi: Patch CMake with WASI platform

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

web-wasi/Dockerfile.in

@@ -26,6 +26,8 @@ ENV AR=${CROSS_ROOT}/bin/llvm-ar \
     CXX=clang++-wasi-sysroot.sh \
     LD=${CROSS_ROOT}/bin/wasm-ld
 
+COPY WASI.cmake /usr/src/
+RUN mv /usr/src/WASI.cmake /usr/share/cmake-*/Modules/Platform/
 COPY Toolchain.cmake ${CROSS_ROOT}/
 ENV CMAKE_TOOLCHAIN_FILE ${CROSS_ROOT}/Toolchain.cmake