Switch to the fastest compression on SPM cache.

.bitrise/bitrise.yml

@@ -66,7 +66,7 @@ workflows:
     steps:
     - save-spm-cache@1:
         inputs:
-        - compression_level: 19
+        - compression_level: 1
     summary: This workflow's only task is to save resolved SPM dependencies to the
       cache to be re-used later by other workflows (mainly the _common_prepare_workspace
       one).