discount: enable parallel builds

pkgs/tools/text/discount/default.nix

@@ -11,7 +11,14 @@ stdenv.mkDerivation rec {
     sha256 = "0p2gznrsvv82zxbajqir8y2ap1ribbgagqg1bzhv3i81p2byhjh7";
   };
 
-  patches = ./fix-configure-path.patch;
+  patches = [
+    ./fix-configure-path.patch
+
+    # Fix parallel make depends:
+    # - https://github.com/Orc/discount/commit/e42188e6c4c30d9de668cf98d98dd0c13ecce7cf.patch
+    # - https://github.com/Orc/discount/pull/245
+    ./parallel-make.patch
+  ];
   configureScript = "./configure.sh";
 
   configureFlags = [
@@ -21,6 +28,7 @@ stdenv.mkDerivation rec {
     "--with-fenced-code"
   ];
 
+  enableParallelBuilding = true;
   doCheck = true;
 
   meta = with lib; {

pkgs/tools/text/discount/parallel-make.patch

@@ -0,0 +1,15 @@
+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