For CI - upgrade to Xcode 7.3.1.

Update the documentation on how to enable ccache for Xcode 7 on OSX with SIP/rootless turned on.

.travis.yml

@@ -325,7 +325,7 @@ after_script: rake ci_teardown_cache
 branch: {name: OSX-CI, active: yes, mandatory: yes}
 language: objective-c
 cache: {directories: $HOME/.ccache}
-osx_image: xcode7.1
+osx_image: xcode7.3
 env:
   global:
     - secure: SLJCjkjDsTMbCIV9Wecz5JATnhk0fuzlnLMeZdvvFDv+8NL8cXyutkU0VfyRSLf3HSD1Js79a6fRMROyVGWj/w/BRrjqGnZzsB6+ZeJNnadiVIF5Gh+w90We5ccvSp2G4DyYgwkNnkKlJK7zNEWGu/K+bHL1EOCA+EIVrFMyA44=
@@ -358,7 +358,7 @@ before_script:
   # for f in $(brew cask list |grep -v Uninstalling); do [[ $whitelist =~ $f ]] || brew cask uninstall --force $f; done
   - brew cleanup
   - export PATH=$(brew info ccache |grep -o '\S*lib\S*'):$PATH
-  - if [ $XCODE ]; then sudo cp -p $(which ccache) $(dirname $(xcodebuild -find-executable clang)) && for compiler in clang clang++; do path=$(xcodebuild -find-executable $compiler); sudo mv $path{,.orig} && sudo ln -sf $(dirname $path)/clang.orig /usr/bin/$compiler && sudo ln -sf ccache $path; done && if [ $IOS ]; then redundant=AppleTV,Watch; elif [ $TVOS ]; then redundant=iPhone,Watch; else redundant=iPhone,AppleTV,Watch; fi && eval sudo rm -rf /Applications/Xcode.app/Contents/Developer/Platforms/{$redundant}{OS,Simulator}.platform; if echo $COMMIT_MESSAGE |egrep -cq '\[(ccache clear|xcode 64bit only)\]' || [[ $(ccache -s |grep 'files in cache' |rev |cut -d' ' -f1 |rev) == '0' ]]; then export XCODE_64BIT_ONLY=1; fi; fi
+  - if [ $XCODE ]; then pushd $(dirname $(xcodebuild -find-executable clang)) && sudo cp -p $(which ccache) . && for compiler in clang clang++; do sudo mv $compiler{,.orig} && sudo ln -sf $(pwd)/clang.orig /usr/local/bin/$compiler && sudo ln -sf ccache $compiler; done && popd && if [ $IOS ]; then redundant=AppleTV,Watch; elif [ $TVOS ]; then redundant=iPhone,Watch; else redundant=iPhone,AppleTV,Watch; fi && eval sudo rm -rf /Applications/Xcode.app/Contents/Developer/Platforms/{$redundant}{OS,Simulator}.platform; if echo $COMMIT_MESSAGE |egrep -cq '\[(ccache clear|xcode 64bit only)\]' || [[ $(ccache -s |grep 'files in cache' |rev |cut -d' ' -f1 |rev) == '0' ]]; then export XCODE_64BIT_ONLY=1; fi; fi
   - rake ci_setup_cache
 script: rake ci && if [ $PACKAGE_UPLOAD ]; then rake ci_package_upload; fi && rake ci_timer
 after_script: rake ci_teardown_cache

Docs/GettingStarted.dox

@@ -368,11 +368,11 @@ for compiler in clang clang++; do mv $compiler{,.orig} && ln -sf $(which ccache)
 On Xcode 6 or above:
 \verbatim
 cd $(dirname $(xcodebuild -find-executable clang))
-cp -p $(which ccache) .
-for compiler in clang clang++; do mv $compiler{,.orig} && sudo mv /usr/bin/$compiler{,.orig} && sudo ln -sf $(pwd)/clang.orig /usr/bin/$compiler && ln -sf ccache $compiler; done
+sudo cp -p $(which ccache) .
+for compiler in clang clang++; do sudo mv $compiler{,.orig} && sudo ln -sf $(pwd)/clang.orig /usr/local/bin/$compiler && sudo ln -sf ccache $compiler; done
 \endverbatim
 
-Starting since version 6, Xcode has done something funky internally. It won't build unless the symlink resolves to an executable within its own rooted-'/usr/bin' in Xcode.app package. The 'ccache' executable is physically copied to this location for this reason. But as the result, you have to manually keep this copy up to date when upgrading 'ccache'.
+Starting since version 6, Xcode has done something funky internally. It won't build unless the symlink resolves to an executable within its own rooted-'/usr/bin' in Xcode.app package. The 'ccache' executable is physically copied to this location for this reason. But as the result, you have to manually keep this copy up to date when upgrading ccache and also repeat the whole process again as necessary when upgrading Xcode.
 
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