[OpenSmalltalk/opensmalltalk-vm] 4a3c9c: Upgrade to xcode8.3

 
  Branch: refs/heads/Cog
  Home:   https://github.com/OpenSmalltalk/opensmalltalk-vm
  Commit: 4a3c9ca1ee43161070b33845068dba9afab77be8
      https://github.com/OpenSmalltalk/opensmalltalk-vm/commit/4a3c9ca1ee43161070b33845068dba9afab77be8
  Author: Fabio Niephaus <[hidden email]>
  Date:   2019-05-29 (Wed, 29 May 2019)

  Changed paths:
    M .travis.yml

  Log Message:
  -----------
  Upgrade to xcode8.3

See: http://forum.world.st/OSX-Build-broken-past-2-months-could-not-find-a-valid-SDK-td5099288.html