LDC: Fix Azure CI for tags and use clang 8.0.0 on Windows

Author: kinke

azure-pipelines.yml

@@ -6,19 +6,16 @@ variables:
 
 # Although tags are supposed to trigger builds by default, they don't.
 trigger:
-  branches:
-    include: ['*']
-  tags:
-    include:
-      - ldc-v*
+- '*'
+- refs/tags/ldc-v*
 
 jobs:
 - job: Windows
   timeoutInMinutes: 180
   pool:
     vmImage: 'vs2017-win2016'
   variables:
-    CLANG_VERSION: 7.0.1
+    CLANG_VERSION: 8.0.0
     VSINSTALLDIR: C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\
     EXTRA_CMAKE_FLAGS: -DLLVM_USE_CRT_RELEASE=MT
   strategy: