CI: Update to LLVM-12

The current stable release of LLVM is 12, update to that.  While at it,
fix that we had not correctly upgraded to LLVM 11 previously.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/.azure-pipelines.yml b/.azure-pipelines.yml
index c088e1a..0cf7302 100644
--- a/.azure-pipelines.yml
+++ b/.azure-pipelines.yml
@@ -2,7 +2,7 @@
   windows_vm: vs2017-win2016
   ubuntu_vm: ubuntu-18.04
   macos_vm: macOS-10.15
-  ci_runner_image: trini/u-boot-gitlab-ci-runner:focal-20210609-06Jul2021
+  ci_runner_image: trini/u-boot-gitlab-ci-runner:focal-20210723-04Aug2021
   # Add '-u 0' options for Azure pipelines, otherwise we get "permission
   # denied" error when it tries to "useradd -m -u 1001 vsts_azpcontainer",
   # since our $(ci_runner_image) user is not root.
@@ -183,7 +183,7 @@
           TEST_PY_BD: "sandbox"
         sandbox_clang:
           TEST_PY_BD: "sandbox"
-          OVERRIDE: "-O clang-10"
+          OVERRIDE: "-O clang-12"
         sandbox_spl:
           TEST_PY_BD: "sandbox_spl"
           TEST_PY_TEST_SPEC: "test_ofplatdata or test_handoff or test_spl"