also set UPDATE_PACKAGE in updater for old recoveries

Change-Id: I90e3feb0c1655279d58751ce800f299d9b4f3d03

updater/updater.c

@@ -63,6 +63,7 @@ int main(int argc, char** argv) {
     // Extract the script from the package.
 
     char* package_data = argv[3];
+    setenv("UPDATE_PACKAGE", package_data, 1);
     ZipArchive za;
     int err;
     err = mzOpenZipArchive(package_data, &za);