build-style qmake: don't use configure_script

When running do_configure(), configure_script is already set to
./configure and we can't set another default.
Thus always use qmake directly.

common/build-style/qmake.sh

@@ -2,14 +2,12 @@
 # This helper is for templates using Qt4/Qt5 qmake.
 #
 do_configure() {
-	configure_script=qmake
-
 	if [ -n "$build_pie" ]; then
-		${configure_script} ${configure_args} \
+		qmake ${configure_args} \
 			QMAKE_LFLAGS_SHLIB+=" -Wl,-z,now" \
 			QMAKE_LFLAGS_PLUGIN+=" -Wl,-z,now"
 	else
-		${configure_script} ${configure_args}
+		qmake ${configure_args}
 	fi
 }