Make dynamic partition control android return a writable fd am: 21a4991833 am: 36e848e8bc am: e6fc9761c9

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/1634739

Change-Id: I1879f5580dcc50ad560f15cbdb47c2d921de69c8
diff --git a/scripts/brillo_update_payload b/scripts/brillo_update_payload
index d1a1781..746cefb 100755
--- a/scripts/brillo_update_payload
+++ b/scripts/brillo_update_payload
@@ -89,12 +89,14 @@
   exit 1
 }
 
-# Loads shflags. We first look at the default install location; then look for
-# crosutils (chroot); finally check our own directory.
+# Loads shflags. We first look at the default install location; then our own
+# directory; finally the parent directory.
 load_shflags() {
   local my_dir="$(dirname "$(readlink -f "$0")")"
   local path
-  for path in /usr/share/misc "${my_dir}"/lib/shflags; do
+  for path in /usr/share/misc \
+    "${my_dir}"/lib/shflags \
+    "${my_dir}"/../lib/shflags; do
     if [[ -r "${path}/shflags" ]]; then
       . "${path}/shflags" || die "Could not load ${path}/shflags."
       return