Issues addressed:
- xcode build failed with
... was built for newer OSX version (10.10) than being linked (10.5)
fixed by setting GYP mac deployment target to the nix value
- a gyp bug when SDKROOT is not set (and removed an orphaned gyp patch
- path to python in generated gyp-mac-tool
- noisy build due to static assert warnings, by silencing warnings
- use of system xcodebuild and libtool replaced by darwin.cctools
c3da83cd40