seafile-seahub: de-couple build a bit more

seafile-seahub's build is a mess.
It hijacks some OpenWrt mk files into the build.

This can be avoided by provided some of the required parameters via
env-vars and patching the env-vars into the build.
Which is what this patch does.

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>

net/seafile-seahub/patches/020-Makefile-fixes.patch

@@ -1,8 +1,8 @@
 --- a/Makefile
 +++ b/Makefile
 @@ -1,3 +1,6 @@
-+include $(TOPDIR)/rules.mk
-+include $(TOPDIR)/feeds/packages/lang/python/python-package.mk
++PYTHON ?= python
++DJANGO_ADMIN_PY ?= django-admin.py
 +
  PROJECT=seahub
  
@@ -12,7 +12,7 @@
  locale:
  	@echo "--> Compile locales"
 -	django-admin.py compilemessages
-+	$(call HostPython,,$(STAGING_DIR)/usr/bin/django-admin.py compilemessages)
++	$(DJANGO_ADMIN_PY) compilemessages
  	@echo ""
  
  uglify:
@@ -21,19 +21,19 @@
  statici18n:
  	@echo "--> Generate JS locale files in static/scripts/i18n"
 -	python manage.py compilejsi18n
-+	$(call HostPython,,manage.py compilejsi18n)
++	$(PYTHON) manage.py compilejsi18n
  
  collectstatic:
  	@echo "--> Collect django static files to media/assets"
  	rm -rf media/assets 2> /dev/null
 -	python manage.py collectstatic --noinput -i admin -i termsandconditions -i app -i sysadmin-app -i build.js
-+	$(call HostPython,,manage.py collectstatic --noinput -i admin -i termsandconditions -i app -i sysadmin-app -i build.js)
++	$(PYTHON) manage.py collectstatic --noinput -i admin -i termsandconditions -i app -i sysadmin-app -i build.js
  
  compressstatic:
  	@echo "--> Compress static files(css) to media/CACHE"
  	rm -rf media/CACHE 2> /dev/null
 -	python manage.py compress
-+	$(call HostPython,,manage.py compress)
++	$(PYTHON) manage.py compress
  
  clean:
  	@echo '--> Cleaning media/static cache & dist'