container/fhs: add constant for /dev/shm/

This is mounted for the default read-only /dev/ when programs want to use shm_open(3). Defining it here is less error-prone and saves the extra append at runtime.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/outcome/spcontainer.go

@@ -116,7 +116,7 @@ func (s *spParamsOp) toContainer(state *outcomeStateParams) error {
 		state.params.Bind(fhs.AbsDev, fhs.AbsDev, std.BindWritable|std.BindDevice)
 	}
 	// /dev is mounted readonly later on, this prevents /dev/shm from going readonly with it
-	state.params.Tmpfs(fhs.AbsDev.Append("shm"), 0, 01777)
+	state.params.Tmpfs(fhs.AbsDevShm, 0, 01777)
 
 	return nil
 }