Ensure make rules are serially executed

Also add note to avoid running make in parallel. The ordering
throughout is currently dependent on serial execution.

Makefile

@@ -6,6 +6,7 @@ SHELL := bash
 .DELETE_ON_ERROR:
 .SUFFIXES:
 .SECONDARY:
+.NOTPARALLEL:
 
 DO = src/ontology/doid
 EDIT = src/ontology/doid-edit.owl
@@ -20,6 +21,8 @@ HD = src/ontology/HumanDO
 # Set the ROBOT version to use
 ROBOT_VRS = 1.9.5
 
+# ***NEVER run make commands in parallel (do NOT use the -j flag)***
+
 # to make a release, use `make release`
 # to update imports, use `make imports`
 # to run QC tests on doid-edit.owl, use `make test`