Xcode 10.0 GM Seed 1 was released on 12 Sep 2018 and requires macOS 10.13.6+.
It can be downloaded from https://download.developer.apple.com/Developer_Tools/Xcode_10_GM_seed/Xcode_10_GM_seed.xip.
The SDKs it contains are:
- iOS 12.0 (Build 16A366)
- macOS 10.14 (Build 18A384)
- tvOS 12.0 (Build 16J364)
- watchOS 5.0 (Build 16R363)
The compilers it contains are:
- clang 10.0.0 (Build 1000.11.45.2)
- swift 4.2 (Build 1000.11.37.1)