BC: Move builddirectory handling into BC itself

Use setBuildDirectory() in the different BuildConfigurations instead
of reimplementing that over and over again.

Change-Id: Ic355fdb4624c71667ce470b3e2865c9a8722ef09
Reviewed-by: Daniel Teske <daniel.teske@digia.com>
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>

src/plugins/qnx/blackberryabstractdeploystep.cpp

@@ -81,7 +81,7 @@ bool BlackBerryAbstractDeployStep::init()
     m_processCounter = -1;
 
     m_environment = target()->activeBuildConfiguration()->environment();
-    m_buildDirectory = target()->activeBuildConfiguration()->buildDirectory();
+    m_buildDirectory = target()->activeBuildConfiguration()->buildDirectory().toString();
 
     return true;
 }