These are compilation failures from simply compiling a lit test before the first transform is applied. This failure doesn't seem to have anything to do with the Migrator, and more to do with the nature of the test. You should get the same result just using clang++ -fsyntax-only. On Linux some of these errors are warnings caused by -Wnon-literal-null-conversion. I've never seen this test fail on windows and it hasn't changed in some time. Looking back through the build history of this builder this test was passing as of http://bb.pgr.jp/builders/ninja-clang-i686-msc17-R/builds/2055. My guess something changed in clang in how it handles this kind of code.
Does clang treat warnings/errors differently on windows than on Linux? Did something change recently in clang that might cause these errors to pop up on windows. I don't see them in Linux with a clean build of llvm/clang/Migrator.