practracker: add envvar TOR_PRACTRACKER_OPTIONS

We have Makefile.am use this to decide how to invoke practracker on
the Tor source.

Makefile.am

@@ -371,7 +371,7 @@ endif
 
 check-best-practices:
 if USEPYTHON
-	@$(PYTHON) $(top_srcdir)/scripts/maint/practracker/practracker.py $(top_srcdir)
+	@$(PYTHON) $(top_srcdir)/scripts/maint/practracker/practracker.py $(top_srcdir) $(TOR_PRACTRACKER_OPTIONS)
 endif
 
 practracker-regen:

changes/ticket31309

@@ -0,0 +1,4 @@
+  o Minor features (best practices tracker):
+    - Add a TOR_PRACTRACKER_OPTIONS variable for passing arguments
+      to practracker from the environment. We may want this for
+      continuous integration. Closes ticket 31309.