(swift-2.0 branch) building Charts.xcodeproj fails (exit code 65) with Release configuration

[creister]

tl;dr changing SWIFT_OPTIMIZATION_LEVEL to "-Onone" fixes xcodebuild failure, but not sure why.

Building from swift-2.0 branch, commit 807156773de48668f9ae06aba30ec5317bca89dd
Using Xcode 7.3 beta

From root project directory:
xcodebuild -scheme Charts -project Charts/Charts.xcodeproj/ -configuration Release

The build fails with exit code 65:

** BUILD FAILED **


The following build commands failed:
    CompileSwift normal arm64 /Users/creisterer/Develop/ios-charts/Charts/Classes/Components/ChartLimitLine.swift
    CompileSwift normal arm64 /Users/creisterer/Develop/ios-charts/Charts/Classes/Data/LineRadarChartDataSet.swift
    CompileSwift normal arm64 /Users/creisterer/Develop/ios-charts/Charts/Classes/Data/CandleChartDataSet.swift
    CompileSwiftSources normal arm64 com.apple.xcode.tools.swift.compiler
(4 failures)

As it succeeds with the Debug configuration I went through the build configuration settings and isolated the SWIFT_OPTIMIZATION_LEVEL setting. Changing this from Fast (-O) to mirror debug (-Onone) fixes this but I'm not sure why.

I first noticed this trying to checkout and build the project with Carthage.

[danielgindi]

You should post in Apple forums - they have experienced some compiler crashes in Xcode 7, and fixed some, but it seems that there are more...