Add install target

Makefile

@@ -1,14 +1,28 @@
 
 LDFLAGS=
-#LDFLAGS=--no-debug
+DESTDIR=/usr
+
+BUILDDIR=_build
 
 all: build
 
-build:
-	crystal build $(LDFLAGS) src/pushokku.cr -o pushokku
+$(BUILDDIR):
+	mkdir -p $(BUILDDIR)
 
+build: clean $(BUILDDIR)
+	crystal build $(LDFLAGS) src/pushokku.cr -o $(BUILDDIR)/pushokku
+
+build-release: LDFLAGS=--release --no-debug
+build-release: build
+
+install:
+	install -m 0755 -o root -g root \
+		$(BUILDDIR)/pushokku \
+		$(DESTDIR)/bin/pushokku
 test:
 
 run:
 	crystal run src/pushokku.cr
 
+clean:
+	rm -f $(BUILDDIR)/pushokku