https://github.com/Orc/discount/pull/245
https://github.com/Orc/discount/commit/e42188e6c4c30d9de668cf98d98dd0c13ecce7cf.patch

Fix parallel make failure: add missing pandoc_headers dependency.
--- a/Makefile.in
+++ b/Makefile.in
@@ -139,7 +139,7 @@ test:	$(PGMS) $(TESTFRAMEWORK) verify
 
 pandoc_headers.o: tools/pandoc_headers.c config.h
 	$(BUILD) -c -o pandoc_headers.o tools/pandoc_headers.c
-pandoc_headers: pandoc_headers.o
+pandoc_headers: pandoc_headers.o $(COMMON) $(MKDLIB)
 	$(LINK) -o pandoc_headers pandoc_headers.o $(COMMON) -lmarkdown 
 
 branch.o: tools/branch.c config.h