helper/proc: pass extra files and start

For integration with native container tooling.

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

internal/executable_test.go

@@ -0,0 +1,17 @@
+package internal_test
+
+import (
+	"os"
+	"testing"
+
+	"git.gensokyo.uk/security/fortify/internal"
+)
+
+func TestExecutable(t *testing.T) {
+	for i := 0; i < 16; i++ {
+		if got := internal.MustExecutable(); got != os.Args[0] {
+			t.Errorf("MustExecutable: %q, want %q",
+				got, os.Args[0])
+		}
+	}
+}