ext: move syscall wrappers from container

These are generally useful, and none of them are container-specific. Syscalls subtle to use and requiring container-specific setup remains in container.

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

cmd/mbf/main.go

@@ -24,6 +24,7 @@ import (
 	"hakurei.app/container/fhs"
 	"hakurei.app/container/seccomp"
 	"hakurei.app/container/std"
+	"hakurei.app/ext"
 	"hakurei.app/internal/pkg"
 	"hakurei.app/internal/rosa"
 	"hakurei.app/message"
@@ -271,7 +272,7 @@ func main() {
 				return errors.New("report requires 1 argument")
 			}
 
-			if container.Isatty(int(w.Fd())) {
+			if ext.Isatty(int(w.Fd())) {
 				return errors.New("output appears to be a terminal")
 			}
 			return rosa.WriteReport(msg, w, cache)