priv/shim: move /sbin/init setup to app

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

internal/linux/interface.go

@@ -19,8 +19,8 @@ type System interface {
 	TempDir() string
 	// LookPath provides [exec.LookPath].
 	LookPath(file string) (string, error)
-	// Executable provides [os.Executable].
-	Executable() (string, error)
+	// MustExecutable provides [proc.MustExecutable].
+	MustExecutable() string
 	// LookupGroup provides [user.LookupGroup].
 	LookupGroup(name string) (*user.Group, error)
 	// ReadDir provides [os.ReadDir].

internal/linux/std.go

@@ -11,6 +11,7 @@ import (
 	"sync"
 	"syscall"
 
+	"git.gensokyo.uk/security/fortify/helper/proc"
 	"git.gensokyo.uk/security/fortify/internal"
 	"git.gensokyo.uk/security/fortify/internal/fmsg"
 )
@@ -32,7 +33,7 @@ func (s *Std) Geteuid() int                                 { return os.Geteuid(
 func (s *Std) LookupEnv(key string) (string, bool)          { return os.LookupEnv(key) }
 func (s *Std) TempDir() string                              { return os.TempDir() }
 func (s *Std) LookPath(file string) (string, error)         { return exec.LookPath(file) }
-func (s *Std) Executable() (string, error)                  { return os.Executable() }
+func (s *Std) MustExecutable() string                       { return proc.MustExecutable() }
 func (s *Std) LookupGroup(name string) (*user.Group, error) { return user.LookupGroup(name) }
 func (s *Std) ReadDir(name string) ([]os.DirEntry, error)   { return os.ReadDir(name) }
 func (s *Std) Stat(name string) (fs.FileInfo, error)        { return os.Stat(name) }