ci: disable building some optional Clang components

This commit disables the Clang static analyzer and ARCMigrate components
of Clang. These aren't used at the moment in TinyGo so don't need to be
enabled. This reduces the build by 200 files (2909 -> 2709).

The idea comes from here (via LLVM weekly):
https://www.cambus.net/speedbuilding-llvm-clang-in-5-minutes/

azure-pipelines.yml

@@ -28,7 +28,7 @@ jobs:
     - task: CacheBeta@0
       displayName: Cache LLVM build
       inputs:
-        key: llvm-build-11-windows-v4
+        key: llvm-build-11-windows-v5
         path: llvm-build
     - task: Bash@3
       displayName: Build LLVM