package/qt5/qt5virtualkeyboard: convert to qmake infrastructure

package/qt5/qt5virtualkeyboard: convert to qmake infrastructure

It seems the old method was missing some files from the install
step since after the conversion the following additional files
appear in target after a build with all config options selected:

usr/lib/qt/plugins/lipi_toolkit/libactivedtw.so
usr/lib/qt/plugins/lipi_toolkit/libboxfld.so
usr/lib/qt/plugins/lipi_toolkit/libl7.so
usr/lib/qt/plugins/lipi_toolkit/liblipiengine.so
usr/lib/qt/plugins/lipi_toolkit/liblogger.so
usr/lib/qt/plugins/lipi_toolkit/libneuralnet.so
usr/lib/qt/plugins/lipi_toolkit/libnn.so
usr/lib/qt/plugins/lipi_toolkit/libnpen.so
usr/lib/qt/plugins/lipi_toolkit/libpointfloat.so
usr/lib/qt/plugins/lipi_toolkit/libpreproc.so
usr/lib/qt/plugins/lipi_toolkit/libsubstroke.so
usr/lib/qt/plugins/virtualkeyboard/libqtvirtualkeyboard_lipi.so

Signed-off-by: Andreas Naumann <anaumann@ultratronik.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>