Revert "Revert "releasetools: Allow using futility-host to sign old TF.zip.""

This reverts commit d6145b6a160a7c171269d9408a675d8ff4f08283.

The cause of the earlier breakage has been identified and fixed by
commit 4b577413ff5c43e9b857f5c1685d6909e7ca27ba.

Bug: 35467608
Test: lunch ryu-userdebug; m dist otatools-package
(cherry picked from commit 4f30f7cfa1a46a90a1c60d81330c45d25c160aa8)
diff --git a/tools/releasetools/common.py b/tools/releasetools/common.py
index a4862a6..43e3870 100644
--- a/tools/releasetools/common.py
+++ b/tools/releasetools/common.py
@@ -497,7 +497,13 @@
   elif info_dict.get("vboot", None):
     path = "/" + os.path.basename(sourcedir).lower()
     img_keyblock = tempfile.NamedTemporaryFile()
-    cmd = [info_dict["vboot_signer_cmd"], info_dict["futility"],
+    # We have switched from the prebuilt futility binary to using the tool
+    # (futility-host) built from the source. Override the setting in the old
+    # TF.zip.
+    futility = info_dict["futility"]
+    if futility.startswith("prebuilts/"):
+      futility = "futility-host"
+    cmd = [info_dict["vboot_signer_cmd"], futility,
            img_unsigned.name, info_dict["vboot_key"] + ".vbpubk",
            info_dict["vboot_key"] + ".vbprivk",
            info_dict["vboot_subkey"] + ".vbprivk",