clangbackend crashing every second; affecting arguments passed to libclang

I have a cuda/c++ file in a cmake project which consistently crashes the clang backend.  I realize cuda may be unsupported, but I've investigated the issue by launching qtcreator with

QTC_CLANG_NO_DIAGNOSTIC_CHECK=1 QTC_CLANG_ENABLE_STACKTRACES=1 QT_LOGGING_RULES='qtc.clang*=true' qtcreator

and setting the clang code model warnings to "-###".  Which has led me to believe the issue stems from libclang being called with "-m32" despite my being on x86-64 and all my build artifacts being 64-bit.

So my issue/question is: how do I affect the arguments that get passed to libclang?  In this case:

Arguments to libclang: -nostdinc -nostdinc++ -fsyntax-only -m32 -std=gnu++2a -fcxx-exceptions -fexceptions -DQ_CREATOR_RUN -D__SSP_STRONG__=3 '-D__DBL_MIN_EXP__=(-1021)'  ...

... plus >12,000 more characters, mostly defining constants.  My cursory look at src/plugins/clangcodemodel/ gives me the impression that they comes from a ToolChainInfo object, but its unclear to me how that is constructed and how it could get detected as 32-bit.