Also:
- upgrade Go: 1.12 > 1.13
- upgrade Android SDK: 28.0.3 > 29.0.2
- nix: stop using system Fastlane for iOS builds
- nix: include CocoaPods in shell for iOS
- nix: concatenate shellHooks correctly
- fix gomobile status-go build by setting GO111MODULE=off
- fix gradle accepting empty STATUS_GO_SRC_OVERRIDE value
- don't use a pure shell for uploadToSauceLabs()
Signed-off-by: Jakub Sokołowski <jakub@status.im>