Provide cached copies of git repositories used (lwip.git offline)

[TD-er]

I had issues fetching platform updates, so I removed the framework dirs in my packages dir.
But now apparently https://git.savannah.nongnu.org/git/lwip.git is down, which means I cannot do anything anymore until that's fixed again. (which as always comes at a very very bad moment)

Is there a possibility to have these cached as a fall-back somewhere and defined them in the json files describing the framework?
I know they are supposed to be stored in my .platformio/packages dir, but that's no longer the case right now... :(

So for future mishaps like these, it would be nice if there is some fallback option somewhere.

[TD-er]

What do I have to change where to get the esp78266/Arduino to be cloned again?
The entire LWIP is not even needed to be cloned anyway, as a pre-compiled version is included.
But PlatformIO refuses to continue and this means I am completely stuck as non of my systems can compile anymore since for whatever reason they all want to download the framework again which fails.