Merge of r20795 - LLDB arch detection

[Sylvestre Ledru]

Hello Tom & others,

I would like to propose the r20795 for merge into both 3.5 & 3.6 LLDB
branches.
It fixes bug http://llvm.org/bugs/show_bug.cgi?id=20400

FYI, I am applying this patch on top of the Debian packages already but
I think
it could save a lot of time to users.

Thanks,
Sylvestre  '