Prevent building with busted xcode tools

[jdm]

We know that a particular version of xcode that is available with MacOS Mojave contains a bug that prevents linking Servo (#21792). We should detect that and tell users attempting to build Servo with that XCode version that they need to update.

It might be possible to use xcode-select --version to detect this. On a system with a busted version, the output is 2354. On my system which is pre-Mojave is it 2347.

[jdm]

@paulrouget What does xcode-select --version show on a system with the xcode beta installed?

[pradyunsg]

The check has to be added in this file, or is there a better place?

https://github.com/servo/servo/blob/master/python/servo/build_commands.py#L200

[jdm]

Yes, that seems fine to me. We have similar checks for known-broken configurations at

servo/python/servo/build_commands.py

Lines 215 to 218 in 55347aa

	# https://github.com/servo/servo/issues/22069
	if debug_mozjs and magicleap:
	print("Please specify either --debug-mozjs or --magicleap.")
	sys.exit(1)

.

[CYBAI]

I remember I'm using Xcode beta on macOS Mojave (10.14.3) but, unfortunately, I see 2354 from xcode-select --version. Not sure if I checked in the right way? 🤔

→ xcode-select -p
/Applications/Xcode-beta.app/Contents/Developer

→ xcode-select --version
xcode-select version 2354.

[jdm]

Humbug. What about dsymutil --version?

[CYBAI]

→ dsymutil --version
Apple LLVM version 10.0.1 (clang-1001.0.37.9)
  Optimized build.
  Default target: x86_64-apple-darwin18.2.0
  Host CPU: skylake

[jdm]

Apple LLVM version 9.0.0 (clang-900.0.39.2)
  Optimized build.
  Default target: x86_64-apple-darwin16.7.0
  Host CPU: haswell

How about yours @pradyunsg?

[pradyunsg]

Apple LLVM version 10.0.0 (clang-1000.11.45.5)
  Optimized build.
  Default target: x86_64-apple-darwin18.2.0
  Host CPU: haswell

[pradyunsg]

Should I try adding homebrew's LLVM to the path? (it does seem insanely fairly old)

$ /usr/local/Cellar/llvm/7.0.1/bin/dsymutil --version
LLVM (http://llvm.org/):
  LLVM version 7.0.1
  Optimized build.
  Default target: x86_64-apple-darwin18.2.0
  Host CPU: haswell

[jdm]

No idea if that will work or not. The supported way is to install the xcode beta.

[pradyunsg]

I'll try after my paper today.

[paulrouget]

xcode-select --version shows 2354 with the beta.

dsymutil --version shows:

Apple LLVM version 10.0.1 (clang-1001.0.37.7)
  Optimized build.
  Default target: x86_64-apple-darwin18.2.0
  Host CPU: skylake

[pradyunsg]

The supported way is to install the xcode beta.

Alrighty then, starting an ~7 hour download then. :)