buster: build cleanups

 * use := for PYTHON3
 * rearrange mlat-client rules to be simpler
 * simplify mlat-client cleanup to avoid invoking setup.py

buster/rules

@@ -7,7 +7,7 @@ export DEB_BUILD_MAINT_OPTIONS = hardening=+all
 DPKG_EXPORT_BUILDFLAGS = 1
 include /usr/share/dpkg/default.mk
 
-PYTHON3=/usr/bin/$(shell py3versions -d)
+PYTHON3 := /usr/bin/$(shell py3versions -d)
 
 VENV=$(CURDIR)/debian/venv
 
@@ -18,11 +18,11 @@ override http_proxy := http://127.0.0.1:9/
 override https_proxy := http://127.0.0.1:9/
 export http_proxy https_proxy
 
-override_dh_auto_clean: clean_tcllauncher clean_dump1090 clean_mlat-client clean_venv clean_piaware clean_dump978
+override_dh_auto_clean: clean_tcllauncher clean_dump1090 clean_mlat-client clean_piaware clean_dump978
 
 override_dh_auto_configure: check_versions configure_tcllauncher
 
-override_dh_auto_build: build_tcllauncher build_dump1090 setup_venv build_cxfreeze build_mlat-client build_dump978
+override_dh_auto_build: build_tcllauncher build_dump1090 build_mlat-client build_dump978
 
 override_dh_auto_install: install_tcllauncher install_dump1090 install_mlat-client install_piaware install_dump978
 
@@ -62,19 +62,15 @@ install_dump978:
 	install -d $(CURDIR)/debian/piaware/usr/lib/piaware/helpers
 	install -t $(CURDIR)/debian/piaware/usr/lib/piaware/helpers dump978/faup978
 
-setup_venv:
+build_mlat-client:
+	# setup venv for mlat-client build
 	$(PYTHON3) -m venv --system-site-packages --without-pip $(VENV)
-
-clean_venv:
-	rm -fr $(VENV)
-
-build_cxfreeze:
+	# build cxfreeze for later packaging of mlat-client
 	cd typing_extensions-3.6.5 && $(VENV)/bin/python setup.py install
 	cd zipp-0.5.0 && $(VENV)/bin/python setup.py install
 	cd importlib_metadata-4.3.1 && $(VENV)/bin/python setup.py install
 	cd cx_Freeze-6.8.3 && $(VENV)/bin/python setup.py install
-
-build_mlat-client:
+	# build mlat-client proper
 	cd mlat-client && $(VENV)/bin/python setup.py install
 
 install_mlat-client:
@@ -84,7 +80,12 @@ install_mlat-client:
 	cp -a $(CURDIR)/freeze-mlat-client/* $(CURDIR)/debian/piaware/usr/lib/piaware/helpers/
 
 clean_mlat-client:
-	cd mlat-client && $(PYTHON3) setup.py clean -a
+	rm -fr mlat-client/build mlat-client/dist
+	rm -fr cx_Freeze-6.8.3/build cx_Freeze-6.8.3/dist
+	rm -fr importlib_metadata-4.3.1/build importlib_metadata-4.3.1/dist
+	rm -fr zipp-0.5.0/build zipp-0.5.0/dist
+	rm -fr typing_extensions-3.6.5/build typing_extensions-3.6.5/dist
+	rm -fr $(VENV)
 
 install_piaware:
 	make -C piaware DESTDIR=$(CURDIR)/debian/piaware install INSTALL_SUDOERS=1 SYSTEMD= SYSVINIT= TCLLAUNCHER=$(CURDIR)/debian/piaware/usr/bin/tcllauncher