Building the clr.runtime subset from a clean build fails with zstd build error

When building clr.runtime from a clean build (instead of clr.native), the build fails with the following error:

```
  CMake Error at _deps/zstd-build/lib/cmake_install.cmake:53 (file):
    file INSTALL cannot find
    "E:/runtime3/artifacts/obj/coreclr/windows.x64.Debug/_deps/zstd-build/lib/zstd_static.lib":
```

cc: @rzikm 