Issue 6075 - Ignore build artifacts (#6076)

Bug Description:
When running the build I noticed some generated files are not included in .gitignore, thereby cluttering and distracting git use during local development.

Fix Description:
Update .gitignore.

Fixes #6075

Reviewed by @progier389

.gitignore

@@ -236,3 +236,7 @@ vendor.tar.gz
 .history
 .vscode/launch.json
 .cargo/config
+/rs/
+/rust-nsslapd-private.h
+/rust-slapi-private.h
+/src/lib389/setup.py