Building Clang on Ubuntu 14.04

Am trying to build Clang on a fresh install of Ubuntu 14.04 following the instructions here:

http://clang.llvm.org/get_started.html

Build fails immediately with

'llvm-build/include/llvm/Support/DataTypes.h:77:3: error: #error “Don’t have a definition for uint64_t on this platform”

error “Don’t have a definition for uint64_t on this platform”’

Obviously I can edit the header, but I’d like to know what’s wrong with the environment that is causing this issue.

uname -a gives

3.19.0-25-generic #26~14.04.1-Ubuntu SMP Fri Jul 24 21:16:20 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

Am using gcc (Ubuntu 4.8.4-2ubuntu1~14.04) 4.8.4

Cheers,
Andrew.