Make download_abi_dills.py handle multiple abi verions not existing

Bug: https://github.com/dart-lang/sdk/issues/36047
Change-Id: Ifc8f92c6c098e86a06b94be153109214ca038eac
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/99090
Reviewed-by: Alexander Markov <alexmarkov@google.com>
Commit-Queue: Liam Appelbe <liama@google.com>
diff --git a/tools/download_abi_dills.py b/tools/download_abi_dills.py
index 6eaa9e6..4530155 100644
--- a/tools/download_abi_dills.py
+++ b/tools/download_abi_dills.py
@@ -45,8 +45,10 @@
   abi_version = int(utils.GetAbiVersion())
   oldest_abi_version = int(utils.GetOldestSupportedAbiVersion())
 
-  # The latest abi version may not have an entry in CIPD yet, so check first.
-  if not findAbiVersion(abi_version):
+  # The latest abi versions may not have an entry in CIPD yet, so check first.
+  while abi_version >= oldest_abi_version:
+    if findAbiVersion(abi_version):
+      break
     abi_version -= 1
 
   return downloadAbiDills(oldest_abi_version, abi_version)