roachprod: make it possible to use -e multiple times

This way it's possible to pass env vars using `-e` assembled from
multiple strings.

Also this fixes how `cassandra` was invoked when `-e` was also
specified.

Release note: None

pkg/cmd/roachprod/install/cassandra.go

@@ -49,7 +49,7 @@ func (Cassandra) Start(c *SyncedCluster, extraArgs []string) {
 				_ = session.Close()
 			}()
 
-			cmd := c.Env + `env ROACHPROD=true cassandra` +
+			cmd := `env ` + c.Env + ` ROACHPROD=true cassandra` +
 				` -Dcassandra.config=file://${PWD}/cassandra.yaml` +
 				` -Dcassandra.ring_delay_ms=3000` +
 				` > cassandra.stdout 2> cassandra.stderr`

pkg/cmd/roachprod/main.go

@@ -80,7 +80,7 @@ var (
 	listMine          bool
 	clusterType       = "cockroach"
 	secure            = false
-	nodeEnv           = "COCKROACH_ENABLE_RPC_COMPRESSION=false"
+	nodeEnv           = []string{"COCKROACH_ENABLE_RPC_COMPRESSION=false"}
 	nodeArgs          []string
 	tag               string
 	external          = false
@@ -175,7 +175,7 @@ Available clusters:
 	}
 	c.Nodes = nodes
 	c.Secure = secure
-	c.Env = nodeEnv
+	c.Env = strings.Join(nodeEnv, " ")
 	c.Args = nodeArgs
 	if tag != "" {
 		c.Tag = "/" + tag
@@ -1777,7 +1777,7 @@ func main() {
 				"start nodes sequentially so node IDs match hostnames")
 			cmd.Flags().StringArrayVarP(
 				&nodeArgs, "args", "a", nil, "node arguments")
-			cmd.Flags().StringVarP(
+			cmd.Flags().StringArrayVarP(
 				&nodeEnv, "env", "e", nodeEnv, "node environment variables")
 			cmd.Flags().StringVarP(
 				&clusterType, "type", "t", clusterType, `cluster type ("cockroach" or "cassandra")`)