Produce a useful error message when trying to run the x86 CDB on an x64 machine

See this very popular Stack Overflow question:

http://stackoverflow.com/questions/9975949/how-to-configure-cdb-in-qt-creator

When trying to debug on a 64-bit Windows (32 bit Creator), I get the following message:

The CDB process terminated.

It's the same thing as mentioned in QTCREATORBUG-16233, just without the crash.

It seems like something that could easily be detectable, such that the user gets a message like:

"The version of CDB used by the current kit is x86-based, but the host machine is x64. Add the correct version in Options > Build & Run > Debuggers and then use it in the current kit by setting Options > Build & Run > Kits > Kit Name > Debugger."