Install rules for .qml files should use source dir as their source, not build dir copies

When doing an install, it relies on the default "ALL" target having brought everything up to date. At the moment, the install rules for qml modules will copy the .qml files from the build directory instead of from the source directory. The build directory copies are only brought up to date when the qmllint target associated with the qml module is brought up to date, but that qmllint target is not part of the default "ALL" target. This can result in installing out-of-date qml files.