use Makefile to use make -j all

Makefile

@@ -0,0 +1,35 @@
+FONTARTS := $(sort \
+		$(patsubst %.otf,%,\
+		$(patsubst %.woff,%,\
+		$(patsubst %.woff2,%,\
+		$(wildcard *.woff2 *.woff *.otf)\
+	))))
+OTFS     := $(patsubst %,%.otf,$(FONTARTS))
+WOFFS    := $(patsubst %,%.woff,$(FONTARTS))
+WOFF2S   := $(patsubst %,%.woff2,$(FONTARTS))
+FONTS    := $(OTFS) $(WOFFS) $(WOFF2S)
+CACHES   := $(patsubst %,%.fc,$(FONTS))
+
+all: fonts caches
+.PHONY: all
+
+fonts: $(FONTS)
+.PHONY: all
+
+caches: $(CACHES)
+.PHONY: all
+	
+%.woff: %.otf
+	sfnt2woff-zopfli "$<"
+
+%.woff2: %.otf
+	woff2_compress "$<"
+
+%.otf.fc: %.otf fc.format
+	> "$@" LANG=C LC_NUMERIC=C fc-scan --format "$$(cat fc.format)" "$<"
+
+%.woff.fc: %.woff fc.format
+	> "$@" LANG=C LC_NUMERIC=C fc-scan --format "$$(cat fc.format)" "$<"
+
+%.woff2.fc: %.woff.fc
+	cp "$<" "$@"

fc.format

@@ -0,0 +1,9 @@
+family=%{family}
+fullname=%{fullname}
+postscriptname=%{postscriptname}
+variable=%{variable}
+slant=%{slant}
+style=%{style}
+weight=%{weight}
+width=%{width}
+

fetchfont.nix

@@ -3,6 +3,7 @@
 ({src ? null , srcs ? null, name ? "", pname ? "", version ? ""}:
 	with pkgs;
 	let
+		escapeShellArg = lib.strings.escapeShellArg;
 		name_ =
 			if "" != name
 			then name
@@ -25,52 +26,59 @@
 					;;
 				esac
 			done
+			>"Makefile"  echo ${escapeShellArg (builtins.readFile ./Makefile)}
+			>"fc.format" echo ${escapeShellArg (builtins.readFile ./fc.format)}
 		'';
 		buildPhase = ''
 			set -e
 			build_dir="$TMPDIR/build"
 			mkdir "$build_dir"
-			find "$source_dir" \( -name \*.otf -or -name \*.ttf -or -name \*.woff -or -name \*.woff2 \) -exec cp \{\} "$build_dir" \;
+			find "$source_dir" \( -name Makefile -or -name fc.format -or -name \*.otf -or -name \*.ttf -or -name \*.woff -or -name \*.woff2 \) -exec cp \{\} "$build_dir" \;
 			cd "$build_dir"
-
+			for f in *.ttf
-			for s in *.otf *.ttf
 			do
-				bn="''${s%.otf}"
+				[ -f "''${f%.ttf}.otf" ] || mv "$f" "''${f%.ttf}.otf"
-				bn="''${bn%.ttf}"
-				if ! [ -e "$bn.woff" ]
-				then
-					echo "sfnt2woff-zopfli $s => $bn.woff"
-					sfnt2woff-zopfli "$s"
-				fi
-				if ! [ -e "$bn.woff2" ]
-				then
-					echo "woff2_compress $s => $bn.woff2"
-					woff2_compress "$s"
-				fi
-			done
-
-			for s in *.otf *.ttf *.woff
-			do
-				fc="`dirname "$s"`/`basename "$s"`.fc"
-				echo "fc-scan $s"
-				LANG=C LC_NUMERIC=C fc-scan --format 'family=%{family}
-fullname=%{fullname}
-postscriptname=%{postscriptname}
-variable=%{variable}
-slant=%{slant}
-style=%{style}
-weight=%{weight}
-width=%{width}
-
-' "$s" > "$fc"
-			done
-			for s in *.woff2
-			do
-				o="`dirname "$s"`/`basename "$s" .woff2`.woff.fc"
-				fc="`dirname "$s"`/`basename "$s"`.fc"
-				cp "$o" "$fc"
 			done
+			make -j all
 		'';
+#			for s in *.otf *.ttf
+#			do
+#				bn="''${s%.otf}"
+#				bn="''${bn%.ttf}"
+#				if ! [ -e "$bn.woff" ]
+#				then
+#					echo "sfnt2woff-zopfli $s => $bn.woff"
+#					sfnt2woff-zopfli "$s"
+#				fi
+#				if ! [ -e "$bn.woff2" ]
+#				then
+#					echo "woff2_compress $s => $bn.woff2"
+#					woff2_compress "$s"
+#				fi
+#			done
+#
+#			for s in *.otf *.ttf *.woff
+#			do
+#				fc="`dirname "$s"`/`basename "$s"`.fc"
+#				echo "fc-scan $s"
+#				LANG=C LC_NUMERIC=C fc-scan --format 'family=%{family}
+#fullname=%{fullname}
+#postscriptname=%{postscriptname}
+#variable=%{variable}
+#slant=%{slant}
+#style=%{style}
+#weight=%{weight}
+#width=%{width}
+#
+#' "$s" > "$fc"
+#			done
+#			for s in *.woff2
+#			do
+#				o="`dirname "$s"`/`basename "$s" .woff2`.woff.fc"
+#				fc="`dirname "$s"`/`basename "$s"`.fc"
+#				cp "$o" "$fc"
+#			done
+#			'';
 		installPhase = ''
 			cd "$TMPDIR"
 			mkdir -p $out/share/{doc/${name_},fonts/{opentype,truetype,WOFF,WOFF2}{,/.fc}}