[XCBuildConfiguration] Support environment variables in #resolve_build_setting

[UnsafePointer]

This should address #508.

[jetersen]

Absolutely awesome!
With this PR xcodeproj covers my use case completely.

bundle exec rspec

xcodeproj variables
  should still resolve xcode build settings
  subtitues variables that are resolved by xcode build settings
  substitues bundle identifiers env variable
  substitues debug env variable
  substitues release env variable

Finished in 0.17304 seconds (files took 0.17947 seconds to load)
5 examples, 0 failures

Output from sample project

What I did not test if it works fastlane and the chosen xcode scheme.

Schemes can have environment variables added on each scheme.

[UnsafePointer]

This won't address the scheme use case, but I believe as far as Xcodeproj goes, this is good enough for build settings resolution. Xcodeproj doesn't know about the scheme you're trying to use, so it's up to fastlane to read that scheme and set up the build environment with those variables before attempting to resolve build settings.

@segiddins what do you think of this?

[jetersen]

@Ruenzuo thought as much 👍 I'll test it and create an issue with fastlane if there's a issue once this is released.

Still somewhat baffled how simple the change was. 💯

[jetersen]

@dantoml Could we have a release with this, pretty please 👍
Minor change, and validated it works.

[dnkoutso]

this test has the same name as the one above

[dnkoutso]

@Ruenzuo can you also rebase?

[endocrimes]

I'm not 100% sure that this is something we should support in Xcodeproj, as it introduces a discrepancy between what gets resolved in ruby, and the model of the project.

[jetersen]

Most Xcodeproj build settings have distinct names to not conflict with any unintended environment variables.

[endocrimes]

@Casz I'm not so worried about accidental conflict, as I am in adding discrepancies between what is resolved in Xcodeproj as is in the model and project itself.

[UnsafePointer]

@dantoml I guess it all depends on what do we want to get from the API. Currently it reads:

# XCBuildConfiguration#resolve_build_setting
# Gets the value for the given build setting considering any configuration
# file present and resolving inheritance between them

You can always use XCBuildConfiguration#build_settings to get the real model, but what I understand from the API is that this method should try to mimic Xcode value resolution.

[tmspzz]

Any plans on merging this?

[dnkoutso]

@Ruenzuo can you rebase this PR please?

[UnsafePointer]

@dnkoutso rebased

[dnkoutso]

@dantoml any objections of merging this? Seems you had some initial concerns to land this.

[dnkoutso]

@Ruenzuo one more rebase please and we can land this sorry, can you please fix the CHANGELOG and move the entry up to the master section?

[dnkoutso]

ping @Ruenzuo one more time

[UnsafePointer]

@dnkoutso rebased

[dnkoutso]

@Ruenzuo thanks!