Makefile: simplify installation from tar file
By moving the binaries to be rooted at `bin/` in the tar file,
installation can be done from a tar file in one fell swoop:
```console
$ make release
$ sudo tar -C /usr/local -xvf releases/containerd-1.0.0-alpha3-72-ge6ba48f2.m.linux-amd64.tar.gz
```
@@ -172,8 +172,9 @@ binaries: $(BINARIES) ## build binaries
release: $(BINARIES)
@echo "$(WHALE) $@"
- @mkdir -p releases/${RELEASE}
- @cp $(BINARIES) releases/$(RELEASE)/
+ @rm -rf releases/$(RELEASE) releases/$(RELEASE).tar.gz
+ @install -d releases/$(RELEASE)/bin
+ @install $(BINARIES) releases/$(RELEASE)/bin
@cd releases/$(RELEASE) && tar -czf ../$(RELEASE).tar.gz *
clean: ## clean up binaries
