git clone https://github.com/WebKit/WebKit.git WebKit
cd WebKit
xcode-select --install
Tools/Scripts/build-webkit --debug
Tools/Scripts/run-safari --debug
En caso de obtener el siguiente error:
xcode-select: error: tool 'xcodebuild' requires Xcode, but active developer directory '/Library/Developer/CommandLineTools' is a command line tools instance
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Xcode 7.0 or later is required to build WebKit.
You have an earlier version of Xcode, thus the build will
most likely fail. The latest Xcode is available from the App Store.
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Es necesario abrir Xcode, ir a Preferencias > Ubicaciones (Pestaña) > Herramientas de Linea de Comando (Selección múltiple) y seleccionar la última versión.
Fuentes: