build: use Golang 1.15 for MS Azure builds

Signed-off-by: deadprogram <ron@hybridgroup.com>

azure-pipelines.yml

@@ -12,7 +12,7 @@ jobs:
   steps:
     - task: GoTool@0
       inputs:
-        version: '1.14.1'
+        version: '1.15'
     - checkout: self
     - task: CacheBeta@0
       displayName: Cache LLVM source