bball_qml: Fix Makefile race

The bbal_qml Makefile tries to copy the bball files into a bin
directrory. However, it might not have be created before, depending on
the execution order of the testcases. Create the bid directory in the 
bball_qml as well if necessary.

Also use the "@" Makefile notation to hide the single steps in the logs.

testcases/bball_qml/Makefile

@@ -2,6 +2,6 @@
 TARGET=bball_sdl
 
 all:
-	cp bball.qml ../bin/
-	cp bball_qml ../bin/
-	chmod +x ../bin/bball_qml
+	@mkdir -p ../bin
+	@cp bball.qml bball_qml ../bin/
+	@chmod +x ../bin/bball_qml