CI: Update to using clang-17

Currently, llvm-17 is the stable release. Update our container and CI to
fetch and use that.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index b23ece3..6930b41 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -251,7 +251,7 @@
 sandbox with clang test.py:
   variables:
     TEST_PY_BD: "sandbox"
-    OVERRIDE: "-O clang-16"
+    OVERRIDE: "-O clang-17"
   <<: *buildman_and_testpy_dfn
 
 sandbox64 test.py:
@@ -262,7 +262,7 @@
 sandbox64 with clang test.py:
   variables:
     TEST_PY_BD: "sandbox64"
-    OVERRIDE: "-O clang-16"
+    OVERRIDE: "-O clang-17"
   <<: *buildman_and_testpy_dfn
 
 sandbox_spl test.py: