helper/proc: move package out of internal

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

helper/proc/self.go

@@ -0,0 +1,26 @@
+package proc
+
+import (
+	"os"
+	"sync"
+
+	"git.gensokyo.uk/security/fortify/internal/fmsg"
+)
+
+var (
+	executable     string
+	executableOnce sync.Once
+)
+
+func copyExecutable() {
+	if name, err := os.Executable(); err != nil {
+		fmsg.Fatalf("cannot read executable path: %v", err)
+	} else {
+		executable = name
+	}
+}
+
+func MustExecutable() string {
+	executableOnce.Do(copyExecutable)
+	return executable
+}