ci: completion/manpage generation script spring cleaning (#795)

* ci: spring cleaning of completions autogen

This commit changes a few things/cleans up stuff:
- Completion and manpage generation now drops the files off in
  `./target/tmp/bottom` rather than arbitrarily in the build directory.
  This was originally done because I was lazy and just needed it to work
  in CI, but it's kinda gross if you want to build the manpages in your
  own directory.
- CI was updated to handle this.
- Only run if the `BTM_GENERATE` env var is actually non-empty.

* docs: update for manpage/completion gen

* ci: auto delete autogen comp/manpage dir

* ci: fix incorrect mv for autogen

The mv was too late, should be earlier in the workflow.

* ci: specify shell in autogen delete

* docs: more updates to manpage/comp docs

* ci: unify env vars

* ci: skip autogen on build-msi

1 files changed, 1 insertions, 1 deletions

diff --git a/.gitignore b/.gitignore
index 6558add1..431f9c97 100644
--- a/.gitignore
+++ b/.gitignore
@@ -34,4 +34,4 @@ deny.toml
 
 # mkdocs
 site/
-docs/site
\ No newline at end of file
+docs/site