fhs: move from container

This package is not container-specific.

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

internal/pkg/exec.go

@@ -17,10 +17,10 @@ import (
 
 	"hakurei.app/check"
 	"hakurei.app/container"
-	"hakurei.app/container/fhs"
 	"hakurei.app/container/seccomp"
 	"hakurei.app/container/std"
 	"hakurei.app/ext"
+	"hakurei.app/fhs"
 	"hakurei.app/message"
 )