As of December 31, 2017, FreeSWITCH is will no longer be tested on OS X Yosemite. Apple dropped support and no longer issues security patches. Homebrew also no longer officially supports Yosemite.
FreeSWITCH installed and worked fine on Yosemite as of the dates below. If desired, follow the Xcode and directory instructions below, then follow the manual installation instructions.