Use the same keys in all stack jobs

Author: jneira

.azure/linux-stack.yml

@@ -30,7 +30,7 @@ jobs:
   steps:
   - task: Cache@2
     inputs:
-      key: '"stack-root" | "$(Agent.OS)" | $(Build.SourcesDirectory)/$(YAML_FILE)'
+      key: '"stack" | "$(Agent.OS)" | $(Build.SourcesDirectory)/$(YAML_FILE)'
       path: .azure-cache
       cacheHitVar: CACHE_RESTORED
     displayName: "Download cache"

.azure/macos-stack.yml

@@ -26,7 +26,7 @@ jobs:
   steps:
   - task: Cache@2
     inputs:
-      key: '"stack-root" | "$(Agent.OS)" | $(Build.SourcesDirectory)/$(YAML_FILE)'
+      key: '"stack" | "$(Agent.OS)" | $(Build.SourcesDirectory)/$(YAML_FILE)'
       path: .azure-cache
       cacheHitVar: CACHE_RESTORED
     displayName: "Download cache"