Building from source requires Xcode (not only Xcode command-line tools)

[jbarrow]

In case anyone runs into the following error when installing from source:

xcrun: error: unable to find utility "metal", not a developer tool or in PATH

It's solvable with instructions from here: gfx-rs/gfx#2309

I had previously only installed Xcode command-line tools (xcode-select --install), but was running into the above error. Installing full Xcode and running:

sudo xcode-select --switch /Applications/Xcode.app/Contents/Developer

Allowed me to install from source (env CMAKE_BUILD_PARALLEL_LEVEL="" pip install -e .)

[awni]

Maybe we should be more explicit with this in install docs

[awni]

Updated the docs and pinned #200