Force odoc support-files regeneration in build-site.sh
Delete odoc.support directories before building so dune re-runs
odoc support-files, picking up any changes to plugin support file
contents (embedded JS/CSS). Without this, dune considers the step
up-to-date because it only tracks the plugin .cma, not the
embedded string contents.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>