+PROJECT_DIRECTORIES := $(shell ls -d */)
+
+# This makefile is potentially infinitely recursive if something really bad
+# happens when determining the set of project directories - hard-abort if
+# more than 10 levels deep to avoid angry emails.
+ifeq ($(MAKELEVEL), 10)
+ $(error EMERGENCY ABORT: INFINITE RECURSION DETECTED)
+endif
+
+# Build each directory sequentially, even if we are building using multiple
+# cores within each project
+.NOTPARALLEL: