compile irony server on mac os x.

irony_mode.sh

# first brew install llvm --with-clang

IRONY_PATH=`ls -1 ~/.emacs.d/elpa/ | grep ^irony | head -n 1`

LLVM_CONFIG=`which llvm-config`

if [ -z $LLVM_CONFIG ]; then
  echo "llvm-config was not found. trying to find it at /usr/local..."
  LLVM_CONFIG=`find /usr/local -type f -name llvm-config | head -n 1`
fi

LIBCLANG_LIBRARY=`$LLVM_CONFIG --libdir`/libclang.dylib
LIBCLANG_INCLUDE=`$LLVM_CONFIG --includedir`

cmake -DCMAKE_INSTALL_RPATH_USE_LINK_PATH=ON \
      -DLIBCLANG_LIBRARY=$LIBCLANG_LIBRARY \
      -DLIBCLANG_INCLUDE_DIR=$LIBCLANG_INCLUDE \
      -DCMAKE_INSTALL_PREFIX\=~/.emacs.d/irony/ ~/.emacs.d/elpa/$IRONY_PATH/server &&\
      cmake --build . --use-stderr --config Release --target install

llvm-config --includedir and --libdir if we have llvm-config available.
I don't know why, but it seems that brew don't link the llvm/{version}/bin.

@pmetzger we can try to find on common places where llvm could be installed.