Document centos dep

- document centos dep
- add `-y` option

Signed-off-by: Xiang Dai <764524258@qq.com>

production/README.md

@@ -71,14 +71,21 @@ $ go build ./cmd/promtail
 ```
 
 On Linux, promtail requires the systemd headers to be installed for
-Journal support. Promtail can be built with Journal support on Ubuntu
-with the following commands:
+Journal support.
+
+With Journal support on Ubuntu, run with the following commands:
 
 ```bash
-$ sudo apt install libsystemd-dev
+$ sudo apt install -y libsystemd-dev
 $ go build ./cmd/promtail
 ```
 
+With Journal support on CentOS, run with the following commands:
+
+```bash
+$ sudo yum install -y systemd-devel
+$ go build ./cmd/promtail
+
 Otherwise, to build promtail without Journal support, run `go build`
 with CGO disabled: