Just wanted to point this out here, in case it hasn't been run into yet. I've filed a bug with MS already, but it might be a warning to anyone thinking about uninstalling their older versions. Workaround was to build lib/TableGen (well, all of LLVM really due to a case of laziness) at /O1 and utils/TableGen at /Od. Turning inline expansion to 0 apparently works as well.
Other than that the ARM assembler / disassembler plays nicely and I was able to produce bitcode with clang and lower it to ARM assembly, as well as use llvm-objdump to disassemble both x86 and ARM PEs (although ARM required a manual arch override). If I can find a subset of the test suite that doesn't require MinGW I'll give it a run on the rasberry pi.