+# By using $(DOCBUILDDIR)/.roff.stamp instead of ${MAN_ROFF_FILES}, we
+# convey to make that a single invocation of this recipe builds all
+# of the roff files. This prevents parallel make from starting an
+# instance of this recipe for each roff file.
+$(DOCBUILDDIR)/.roff.stamp: ${MAN_RST_FILES}