DebuggerItem: Fix restoration of ABIs

We want to restore even partially valid ABIs (e.g. those where
we are not 100% sure about the supported word width).

This change fixes Mingw compilers that went missing from their kits
after creator was reopened: The ABI did not get restored due to the
word width not being set and the default host ABI was set instead.
This then made the debugger no longer a match (msvc20x does not match
msys!) and thus getting removed from its kit.

Task-number: QTCREATORBUG-10463
Change-Id: Ie89c7aed2f092f3032860915c74655ff70dae77d
Reviewed-by: hjk <hjk121@nokiamail.com>