Set working directory explicitly when running git command

[tmvkrpxl0]

I recently tried to include Create using composite build but it tried to run git command from my root project, not inside of Create.
This PR sets working directory when running git command so that it can be included to elsewhere more easily.
Closes #10122

[tmvkrpxl0]

Also should I change usages of runtimeOnly? It doesn't just mean it'd be included when you launch Minecraft in Create source. It also means that dependency is needed at runtime and it's transitive. For example one of runtimeOnly dependency "Architectury" will be downloaded if other project depends on Create without setting transitive = false and it will show up in mods tab when they launch Minecraft.
It's recommended to create new configuration just for adding other mods.