Buildbot on windows is failing

[Rafael Espíndola]

>   Command 2: "env" "TMPDIR=C:\public\zorg\buildbot\smooshlab\slave-0.8\build\clang-build\178209\tools\clang\test\Driver\Output\crash-report.c.tmp" "TEMP=C:\public\zorg\buildbot\smooshlab\slave-0.8\build\clang-build\178209\tools\clang\test\Driver\Output\crash-report.c.tmp" "TMP=C:\public\zorg\buildbot\smooshlab\slave-0.8\build\clang-build\178209\tools\clang\test\Driver\Output\crash-report.c.tmp" "RC_DEBUG_OPTIONS=1" "not" "C:/public/zorg/buildbot/smooshlab/slave-0.8/build/clang-build/178209/bin/Debug/clang.EXE" "-fsyntax-only" "C:\public\zorg\buildbot\smooshlab\slave-0.8\build\src\tools\clang\test\Driver\crash-report.c" "-F/tmp/" "-I" "/tmp/" "-idirafter" "/tmp/" "-iquote" "/tmp/" "-isystem" "/tmp/" "-iprefix" "/the/prefix" "-iwithprefix" "/tmp" "-iwithprefixbefore" "/tmp/" "-internal-isystem" "/tmp/" "-internal-externc-isystem" "/tmp/" "-DFOO=BAR"
>   Command 2 Result: 0
>   Command 2 Output:
>   None
>
>   Command 2 Stderr:
>   None

So far the log I got matches.

>   Command 3: "cat" "C:\public\zorg\buildbot\smooshlab\slave-0.8\build\clang-build\178209\tools\clang\test\Driver\Output\crash-report.c.tmp.log"
>   Command 3 Result: 0
>   Command 3 Output:
>
>
>   Command 3 Stderr:

This is the part that is strange. Looks like clang is exiting with an
error (since the previous command passed) but not printing anything.
On my VM I get

clang.EXE: warning: argument unused during compilation:
'-internal-isystem C:/Users/ESPIND~1/AppData/Local/Temp/'
clang.EXE: warning: argument unused during compilation:
'-internal-externc-isystem C:/Users/ESPIND~1/AppData/Local/Temp/'
Stack dump:
....

Could you please run the clang invocation in a debugger and see what
is causing it to exit without printing anything? The public bots with
similar setup are also green:

http://bb.pgr.jp/builders/ninja-clang-i686-msc17-R

Cheers,
Rafael