makefile improvements

Makefile

@@ -1,5 +1,7 @@
 DC = dmd
 DFLAGS = -wi -g
+BUILD_DIR = build
+INSTALL_DIR = /usr/local/bin
 
 debug: DFLAGS += -debug
 debug: all
@@ -11,18 +13,23 @@ all: promptd-path promptd-vcs
 
 package: clean release
 	mkdir promptd
-	cp promptd-path promptd-vcs promptd
+	cp $(BUILD_DIR)/promptd-path $(BUILD_DIR)/promptd-vcs promptd
 	tar cf promptd.tar promptd
 	gzip -f9 promptd.tar
 	rm -r promptd
 
 promptd-path: promptd-path.d help.d
-	$(DC) $(DFLAGS) -of$@ $^
+	@mkdir -p $(BUILD_DIR)
+	$(DC) $(DFLAGS) -of$(BUILD_DIR)/$@ $^
 
 promptd-vcs: promptd-vcs.d help.d vcs.d time.d color.d git.d
-	$(DC) $(DFLAGS) -of$@ $^
+	@mkdir -p $(BUILD_DIR)
+	$(DC) $(DFLAGS) -of$(BUILD_DIR)/$@ $^
+
+install: clean release
+	cp $(BUILD_DIR)/promptd-path $(BUILD_DIR)/promptd-vcs $(INSTALL_DIR)
 
 clean:
-	rm -f promptd-path promptd-vcs *.o
+	rm -rf $(BUILD_DIR)
 
-.PHONY: clean debug release all package
+.PHONY: clean debug release all package install