bugfix(?): Write user-provided generated .gitignore content after the API-provided content

[ulucs]

The GitignoreSync task pulls .gitignore data from three different sources: From the user, build process-defined generated_content and API-provided gitignore_io_tokens. This change prints generated_content after gitignore_io_tokens, allowing build setups to overwrite API-provided content (for example, adding !Cargo.lock to generated_content to allow users to commit Cargo lockfiles by overriding the API-provided Rust .gitignore)

[NiklasRosenstein]

The generated content is first because .gitignore applies in order from top to bottom.

# .gitignore
Cargo.lock
!Cargo.lock

Will not ignore Cargo.lock, wheras this will:

# .gitignore
!Cargo.lock
Cargo.lock

[NiklasRosenstein]

(Side note: The uv-installer job is flaky, you can ignore it failing)

[ulucs]

The generated content is first because .gitignore applies in order from top to bottom.

# .gitignore
Cargo.lock
!Cargo.lock

Will not ignore Cargo.lock, wheras this will:

# .gitignore
!Cargo.lock
Cargo.lock

yes, currently the .gitignore sync is set up like this:

<build-process defined lines>
<API-provided lines>
<user-provided lines>

This PR changes it to

<API-provided lines>
<build-process defined lines>
<user-provided lines>

so that the build-process can override the API-provided defaults

[ulucs]

I have edited my initial comment to be clearer on this