Upload generated docs during docs presubmit. (#2825)

Tested:
https://buildkite.com/bazel-testing/bazel-bazel/builds/9943#01a03ec8-ce77-4538-8f56-3d0c527dbce5

mintlify/check_docs.sh

diff --git a/mintlify/check_docs.sh b/mintlify/check_docs.sh
index 6a9de1e..2d79626 100644
--- a/mintlify/check_docs.sh
+++ b/mintlify/check_docs.sh
@@ -16,7 +16,11 @@
   bazel --quiet build \
     //src/main/java/com/google/devtools/build/lib:gen_mdx_reference_docs
 
-  unzip -q bazel-bin/src/main/java/com/google/devtools/build/lib/mdx-reference-docs.zip -d "$DOCS_DIR"
+  ARCHIVE=bazel-bin/src/main/java/com/google/devtools/build/lib/mdx-reference-docs.zip
+
+  buildkite-agent artifact upload "$ARCHIVE" || echo "--- [nonblocker] FYI: Docs upload failed"
+
+  unzip -q "$ARCHIVE" -d "$DOCS_DIR"
 
   cd "$DOCS_DIR"