no way to specify librarian flags

I got bitten by a problem similar to this

So I need to explicitly set /MACHINE for a static library.
It seems like the undocumented QMAKE_LIBFLAGS works in nmake mode but it's completely ignored for VS project files.
I tried 'QMAKE_LIBFLAGS += $${QMAKE_LFLAGS}' but of course this is flawed since LFLAGS_RELEASE and so on isn't included.

I don't know how much overlap there is for link and lib commandline flags but at least some of them are the same, like the needed /MACHINE option.
So maybe qmake could extract relevant options from LFLAGS or provide some other way to properly specify librarian flags without too much redundancy.