Here's a sample .vimrc for Mac:
let $MYCLANGLIBPATH="/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/"
let $MYVIMFILES="~/Dropbox/Settings/vimfiles"
source $MYVIMFILES/vimrc
...and for Windows:
let $MYCLANGLIBPATH="C:/Program Files (x86)/LLVM/bin"
let $MYVIMFILES="$HOME/Dropbox/Settings/vimfiles"
source $MYVIMFILES/vimrc