Ksshaskpass's build system uses CMake.
So to compile Ksshaskpass first create a build dir (cmake does not support
building in the source dir):

  mkdir build
  cd build

then run cmake:

  cmake ..

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

Finally build Ksshaskpass:

  make

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

  make install

(Text more or less copied from the Soprano build instructions.)