Use the magic of character entities!
> or >
< or <
" or "
' or '
& or &
Output:
> or >
< or <
" or "
' or '
& or &
<Exec Command='"C:\Program Files (x86)\Microsoft Visual Studio
9.0\Common7\IDE\devenv.exe" /build "Release|x86" ..\MySolution.sln > log.txt'/>