Polkit-qt's build system uses cmake.

So to compile Polkit-qt first create a build dir

  mkdir build
  cd build

then run cmake:

  cmake ..

(a typical cmake option that is often used is: -DCMAKE_INSTALL_PREFIX=<prefix>)

cmake then presents a configuration summary. At this point you may
want to install missing dependancies (if you do, remove the CMakeCache.txt)
and run cmake again.

Finally build Polkit-qt:

  make

And install it (in most cases root privileges are required):

  make install

That's all :)