Makefiles are now better at handling -j.

src/Makefile

@@ -22,15 +22,20 @@ FRAMEWORKS = -framework AppKit -framework ServiceManagement
 
 LIBS = -lzip
 
-zip:
+default: prereq zip cmdbar_updater $(EXEC).app
+
+prereq:
+	@mkdir -p arm64 x86_64
+
+zip: prereq
 	@$(MAKE) -C libs/Zip/Zip FLAGS=$(FLAGS) CFLAGS=$(CFLAGS) \
-		MACOS_VERSION=$(MACOS_VERSION) all
+		MACOS_VERSION=$(MACOS_VERSION)
 
 cmdbar_updater:
-	@$(MAKE) -C updater FLAGS=$(FLAGS) all
+	@$(MAKE) -C updater FLAGS=$(FLAGS)
 	@cp updater/$@ .
 
-./arm64/%.o: %.swift
+./arm64/%.o: %.swift zip
 	swift -frontend -c $(if $(DEBUG), -D DEBUG,) \
 		-target arm64-apple-macos$(MACOS_VERSION) $(FLAGS) \
 		-I./libs/Zip/Zip -I./libs/Zip/Zip/arm64 -L./libs/Zip/Zip/arm64 \
@@ -38,7 +43,7 @@ cmdbar_updater:
 		-sdk $(SDK) -module-name $(EXEC) -o $@ -emit-module && touch $@
 
 ifdef UNIVERSAL
-./x86_64/%.o: %.swift
+./x86_64/%.o: %.swift zip
 	@swift -frontend -c $(if $(DEBUG), -D DEBUG,) \
 		-target x86_64-apple-macos$(MACOS_VERSION) $(FLAGS) \
 		-I./libs/Zip/Zip -I./libs/Zip/Zip/x86_64 -L./libs/Zip/Zip/x86_64 \
@@ -92,11 +97,8 @@ $(EXEC).app: $(EXEC)
 		    codesign -s ${APPLE_DEVELOPER_ID_APPLICATION} -f --timestamp \
 				-o runtime $(EXEC).app)
 
-all: zip cmdbar_updater $(EXEC).app
-
 clean:
 	rm -rf $(EXEC) $(EXEC).app cmdbar_updater arm64 x86_64
-	mkdir arm64 x86_64
 
 clean-all: clean
 	$(MAKE) -C libs/Zip/Zip clean-all