[build2] Using build2 with clang 6 (trunk) on windows

[Boris Kolpackov]

Username I Wanted Was Already Taken <usernameiwantedwasalreadytaken at gmail.com> writes:

> trace: main:   out_base:  C:\Tests\Build2\hello\clang-6\
> trace: main:   src_base:  ../hello/
> trace: main:   out_root:  C:\Tests\Build2\hello\clang-6\
> trace: main:   src_root:  ../hello/
>
> ../hello/build\root.build:1:7: error: cc and bin module target mismatch

BTW, I've noticed these ugly mixed-slash paths in your output
but I don't believe it's build2's doing. You've hacked up the
build/bootstrap/src-root.build file to use relative paths,
haven't you?