When running clang with an arm triple such as '--target=thumbv7m-none-eabi'

that has a thumb only CPU by default (cortex-m3), and when using the assembler,
the default thumb state of the CPU does not get passed via the triple to LLVM:

$ clang -target thumbv7m-none-eabi -c -v test.s
clang -cc1as ... -triple armv7m-none--eabi ... test.s

Differential Revision: http://reviews.llvm.org/D14121

llvm-svn: 251507