[cfe-dev] Querying a compiler switch setting in clang

[Nat! via cfe-dev]

Hi

I would like to query at certain points in unfortunately various files
like SemaExpr.cpp or CGCall.cpp the value of a compiler flag and branch
accordingly to custom code.

The specific flag I want to query the value of is -fobjc-runtime.

I have now spent some time in various corners of clang, certainly not
all, but I haven't come across that yet, except possibly LangOptions. 
Maybe extending LangOptions would be the best place, but I don't know.

Thanks for a clue.

Ciao
     Nat!