Dinamically search for rcc

- the call for rcc was hard coded in the Makefile. Instead we need
  to search for other options, rcc rcc4 rcc-qt4, just like we do for
  qmake and moc
Derive rcc/moc location from qmake

- Instead of looking for all of the Qt binaries
  we should only search for qmake, and them query
  qmake for the location of the other binaries.