container: use /proc/self/exe directly

This is a more reliable form of pathname to self and also cheaper than os.Executable.

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

cmd/sharefs/fuse.go

@@ -33,6 +33,7 @@ import (
 
 	"hakurei.app/container"
 	"hakurei.app/container/check"
+	"hakurei.app/container/fhs"
 	"hakurei.app/container/std"
 	"hakurei.app/hst"
 	"hakurei.app/internal/helper/proc"
@@ -441,12 +442,7 @@ func _main(s ...string) (exitCode int) {
 		// keep fuse_parse_cmdline happy in the container
 		z.Tmpfs(check.MustAbs(container.Nonexistent), 1<<10, 0755)
 
-		if a, err := check.NewAbs(container.MustExecutable(msg)); err != nil {
-			log.Println(err)
-			return 5
-		} else {
-			z.Path = a
-		}
+		z.Path = fhs.AbsProcSelfExe
 		z.Args = s
 		z.ForwardCancel = true
 		z.SeccompPresets |= std.PresetStrict