qt-creator: avoid conflicts with meta-qt5's qt5-creator

We avoid conflicts by installing no files to sysroot. This causes no fallout
because nothing depends on qt5-creator (if something included later depending
on qt-creator it should depend on qt5-creator).
Note that

| WARNING: QA Issue: qt5-creator rdepends on qt-creator, but it isn't a build dependency? [build-deps]

is a false positve because the names of the libraries are same as for
qt5-creator (see test below).

This patch was tested by:

1. building qt-creator from scratch
2. building an image containing qt5-creator.
   * qt5-creator did not fail for sysroot conflicts
   * image was build without pulling qt-creator

Signed-off-by: Andreas Müller <schnitzeltony@googlemail.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>