Store generated binaries in the cocoapods cache

[acecilia]

Instead of rebuilding the binary every time a new binary is needed, it is possible to speed up the process by:

• When building the binary for the first time, add the compiled binaries to the cocoapods cache (https://guides.cocoapods.org/terminal/commands.html#pod_cache_list).
• When pod install is executed, if the binary is not in the Pods/_Prebuild subfolder:
  • Check if it is in the cocoapods cache. If yes, just copy it from the cache to the Pods/_Prebuild subfolder.
  • If the binary is not found in the cache, build it and add it to the cache.

This functionality may be implemented in a similar way as Accio has already done: https://github.com/JamitLabs/Accio/blob/stable/Sources/AccioKit/Services/FrameworkCachingService.swift#L16

[acecilia]

Ups, I just saw this is already raised in #37