qt: remove TARGET_CONFIGURE_OPTS from make invocation

All compiler options, switches and path settings are done in the
configure step. For the compile and install step there is no need
for the TARGET_CONFIGURE_OPTS variables.

Signed-off-by: Michael Roth <mroth@nessie.de>
Acked-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>