This makes the port install drop the CMake install files into the
sysroot, which is friendlier to macOS users. Homebrew CMake really
likes to pick homebrew zstd, even for cross-builds.
We don't support hashes from external files (anymore), downloading
another file for integrity validation is pointless. As as result, these
two ports would refuse to build as their hashes were missing.
Fixes#6645.