Prerequisites

• Install Xcode (Avaliable on the Mac App Store)
• Install Xcode Command Line Tools (Preferences > Downloads)
• Install depot_tools
• git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git
• sudo nano ~/.bash_profile
• Add export PATH=/path/to/depot_tools:"$PATH" (it's important that depot_tools comes first here)
• source ~/.bash_profile
• From the directory you want to install V8 into, run gclient

Build V8

• fetch v8
• cd v8
• gclient sync
• gclient config https://chromium.googlesource.com/v8/v8
• tools/dev/v8gen.py x64.optdebug
• ninja -C out.gn/x64.optdebug (prepare for lots of fan noise)

• sudo nano ~/.bash_profile
• Add alias d8=/path/to/v8/repo/out.gn/x64.optdebug/d8
• Add alias tick-processor=/path/to/v8/repo/tools/mac-tick-processor
• Add export D8_PATH="/path/to/v8/repo/out.gn/x64.optdebug"
• source ~/.bash_profile