change config.toml to bootstrap.toml for bootstrap module

.gitignore

@@ -1,6 +1,6 @@
 # This file should only ignore things that are generated during a `x.py` build,
 # generated by common IDEs, and optional files controlled by the user that
-# affect the build (such as config.toml).
+# affect the build (such as bootstrap.toml).
 # In particular, things like `mir_dump` should not be listed here; they are only
 # created during manual debugging and many people like to clean up instead of
 # having git ignore such leftovers. You can use `.git/info/exclude` to
@@ -34,6 +34,7 @@ Session.vim
 !/tests/run-make/thumb-none-qemu/example/.cargo
 
 ## Configuration
+/bootstrap.toml
 /config.toml
 /Makefile
 config.mk