Travis CI (#38951)

* travis.yml: xcode9

* before_script.sh: use vendored ruby

.travis.yml

@@ -5,7 +5,7 @@ sudo: true
 matrix:
   include:
     - os: osx
-      osx_image: xcode8.3
+      osx_image: xcode9
       rvm: system
   fast_finish: true
 

ci/travis/before_script.sh

@@ -22,9 +22,9 @@ run export MERGE_BASE="${MERGE_BASE}"
 run export TRAVIS_COMMIT_RANGE="${MERGE_BASE}...${BRANCH_COMMIT}"
 
 # capture system ruby and gem locations
-run export SYSTEM_RUBY_HOME="/System/Library/Frameworks/Ruby.framework/Versions/Current"
-run export SYSTEM_RUBY_BINDIR="${SYSTEM_RUBY_HOME}/usr/bin"
-run export SYSTEM_GEM_HOME="$(gem_homes="${SYSTEM_RUBY_HOME}/usr/lib/ruby/gems/"*; echo ${gem_homes[${#gem_homes[@]}-1]})"
+run export SYSTEM_RUBY_HOME="/usr/local/Homebrew/Library/Homebrew/vendor/portable-ruby/2.3.3"
+run export SYSTEM_RUBY_BINDIR="${SYSTEM_RUBY_HOME}/bin"
+run export SYSTEM_GEM_HOME="$(gem_homes="${SYSTEM_RUBY_HOME}/lib/ruby/gems/"*; echo ${gem_homes[${#gem_homes[@]}-1]})"
 run export SYSTEM_GEM_BINDIR="${SYSTEM_GEM_HOME}/bin"
 
 # capture user gem locations
@@ -36,7 +36,7 @@ run export GEM_PATH="${GEM_HOME}:${SYSTEM_GEM_HOME}"
 run export PATH="${GEM_BINDIR}:${SYSTEM_GEM_BINDIR}:${SYSTEM_RUBY_BINDIR}:${PATH}"
 
 # ensure that brew uses the ruby we want it to
-run export HOMEBREW_RUBY_PATH="${SYSTEM_RUBY_BINDIR}/ruby"
+#run export HOMEBREW_RUBY_PATH="${SYSTEM_RUBY_BINDIR}/ruby"
 
 # make sure brew is on master branch
 run export HOMEBREW_DEVELOPER=1