As of December 31, 2018, FreeSWITCH is no longer tested on OS X El Capitan. Apple dropped support and no longer issues security patches. Homebrew also no longer officially supports El Capitan.
FreeSWITCH installed and worked fine on El Capitan as of the dates below. If desired, follow the Xcode instructions below, then follow the manual installation instructions.
Xcode takes a while to download and is placed into the Applications folder (/Applications directory) with the Command Line Tools in /Applications/Xcode.app/Contents/Developer.
The Xcode Downloads require you to sign in with your Apple ID and agree to the Software Agreement:
El Capitan 10.11: download and install Xcode 7.3.1 from Xcode 7.3.1 Download then start Xcode. NOTE: Xcode 8 CANNOT be used. See FS-9521.
For OS X 10.11 and 10.12: NEVER delete the /usr/local directory! It's very difficult to recreate, it must be restored from a backup. This is due to System Integrity Protection (aka rootless) security.
As of July 17, 2016, this the page below is no longer maintained by the original author and is marked as archived. It is replaced by these instructions: macOS Developer Tools.