Phonon linking problem

[tbscope]

Is there a qmake flag that I can manually invoke for libphonon?

I'm not sure what you mean, but I guess no.
You include the phonon library with QT += phonon

What you see are linker errors which means that the linker can't find certain symbols in the phonon library.
This in turn means that the library isn't found or it is compiled with another compiler (symbols are messed up).

Since neither case describes your problem, I'm out of ideas.
Can you please give more information? Describe exactly what you downloaded, every step you did between installing what you downloaded and building your program, including the full source code.