Try enabling lld

[jdm]

This is an experiment.

---

This change is 

[bors-servo]

☔ The latest upstream changes (presumably #172) made this pull request unmergeable. Please resolve the merge conflicts.

[nox]

Would that improve build speeds? If so, what are we waiting for? 😁

[jdm]

We were waiting for CI to actually work.

[nox]

What happens if this uses lld but not the rest of our stuff btw? Isn't that a problem?

[jdm]

Fun fact: we use lld on Windows for everything already!

[nox]

I'm a bit confused but I guess that wasn't my business anyway: I'm just wondering what's going on if we hardcode that flag in, but cargo itself doesn't use lld for its own linking step.

[jdm]

We already tell cargo to use lld on Windows in Servo's .cargo/config.

[nox]

We already tell cargo to use lld on Windows in Servo's .cargo/config.

Sure, what I meant to say is: lld probably shouldn't be hardcoded here, we should probably pass RUSTC_LINKER or something like that.

RUSTC_LINKER - The path to the linker binary that Cargo has resolved to use for the current target, if specified. The linker can be changed by editing .cargo/config; see the documentation about cargo configuration for more information.

[jdm]

Windows CI failed with:

Traceback (most recent call last):
  File "c:/projects/mozjs/mozjs/js/src/../../configure.py", line 127, in <module>
    sys.exit(main(sys.argv))
  File "c:/projects/mozjs/mozjs/js/src/../../configure.py", line 29, in main
    sandbox.run(os.path.join(os.path.dirname(__file__), 'moz.configure'))
  File "c:\projects\mozjs\mozjs\python\mozbuild\mozbuild\configure\__init__.py", line 409, in run
    self._value_for(option)
  File "c:\projects\mozjs\mozjs\python\mozbuild\mozbuild\configure\__init__.py", line 477, in _value_for
    return self._value_for_option(obj)
  File "c:\projects\mozjs\mozjs\python\mozbuild\mozbuild\util.py", line 944, in method_call
    cache[args] = self.func(instance, *args)
  File "c:\projects\mozjs\mozjs\python\mozbuild\mozbuild\configure\__init__.py", line 542, in _value_for_option
    % option_string.split('=', 1)[0])
mozbuild.configure.options.InvalidOptionError: --enable-linker is not available in this configuration
mozmake: *** [maybe-configure] Error 1
thread 'main' panicked at 'assertion failed: result.success()', build.rs:142:5

No idea why.

[jdm]

Caused by

mozjs/mozjs/build/moz.configure/toolchain.configure

Lines 1907 to 1910 in b2f8393

	@depends(target)
	def is_linker_option_enabled(target):
	if target.kernel not in ('WINNT', 'SunOS'):
	return True

.

[micwoj92]

This branch has conflicts that must be resolved