Update ONNX installing script (#21044)
Avoid using command line flags to pass in CMAKE_PREFIX_PATH. Use
environment variables instead.
Because, otherwise the value of CMAKE_PREFIX_PATH could get encoded
twice. For example, if the prefix is `C:\a\root`, then in
tools/ci_build/github/windows/helpers.ps1 we set it in Env:CMAKE_ARGS
which will be consumed by ONNX. Then when ONNX get it and decoded it,
ONNX will get `C:aroot` instead. Then because the path doesn't exist,
the CMAKE_PREFIX_PATH couldn't take effect when the script installs
ONNX. This PR fixes the issue.
The issue got discovered when I tried to upgrade cmake to a newer
version. Now our Windows CPU CI build pipeline uses cmake 3.27. In the
main branch even the CMAKE_PREFIX_PATH setting does not work, cmake
still can find protoc.exe from the directories. However, starting from
3.28 cmake changed it. With the newer cmake versions the find_library(),
find_path(), and find_file() cmake commands no longer search in
installation prefixes derived from the PATH environment variable.
