debian: fix install location of python files

Debian use /usr/lib/python*/dist-packages (instead of site-packages) for
packaged python modules. It's achieved using --install-layout=deb
option, so pass it on Debian build.

debian/rules

@@ -13,5 +13,5 @@ override_dh_auto_build:
 	make all LIBDIR=/usr/lib DEBIANBUILD=1
 
 override_dh_auto_install:
-	make install LIBDIR=/usr/lib DEBIANBUILD=1 
+	make install LIBDIR=/usr/lib DEBIANBUILD=1 PYTHON_PREFIX_ARG=--install-layout=deb
 	make install-debian-kernel-support LIBDIR=/usr/lib DEBIANBUILD=1 

imgconverter/Makefile

@@ -7,7 +7,7 @@ clean:
 .PHONY: clean
 
 install:
-	python setup.py install -O1 --skip-build --prefix=/usr --root $(DESTDIR)
+	python setup.py install -O1 --skip-build $(PYTHON_PREFIX_ARG) --root $(DESTDIR)
 #ifeq (1,${DEBIANBUILD})
 #	cp *.py $(DESTDIR)/$(PYTHON_SITEARCH)/qubes/
 #else