Release 2020-08-26 toolchain for macOS. (#526)

swiftlang/swift@48350ec
tensorflow/swift-apis@897bac9

Author: dan-zheng

Installation.md

@@ -114,7 +114,7 @@ To install Swift for TensorFlow, download one of the packages below and follow t
 
 | Download |
 |----------|
-| [Xcode 12 (August 19, 2020)](https://storage.googleapis.com/swift-tensorflow-artifacts/macos-toolchains/swift-tensorflow-DEVELOPMENT-2020-08-19-a-osx.pkg) |
+| [Xcode 12 (August 26, 2020)](https://storage.googleapis.com/swift-tensorflow-artifacts/macos-toolchains/swift-tensorflow-DEVELOPMENT-2020-08-26-a-osx.pkg) |
 | [Ubuntu 18.04 (CPU) (Nightly)](https://storage.googleapis.com/swift-tensorflow-artifacts/nightlies/latest/swift-tensorflow-DEVELOPMENT-ubuntu18.04.tar.gz) |
 | [Ubuntu 18.04 (CPU, CUDA 10.2) (Nightly)](https://storage.googleapis.com/swift-tensorflow-artifacts/nightlies/latest/swift-tensorflow-DEVELOPMENT-cuda10.2-cudnn7-ubuntu18.04.tar.gz) |
 | [Ubuntu 18.04 (CPU, CUDA 10.1) (Nightly)](https://storage.googleapis.com/swift-tensorflow-artifacts/nightlies/latest/swift-tensorflow-DEVELOPMENT-cuda10.1-cudnn7-ubuntu18.04.tar.gz) |
@@ -129,6 +129,7 @@ To install Swift for TensorFlow, download one of the packages below and follow t
 
 | Download |
 |----------|
+| [August 19, 2020](https://storage.googleapis.com/swift-tensorflow-artifacts/macos-toolchains/swift-tensorflow-DEVELOPMENT-2020-08-19-a-osx.pkg) |
 | [August 18, 2020](https://storage.googleapis.com/swift-tensorflow-artifacts/macos-toolchains/swift-tensorflow-DEVELOPMENT-2020-08-18-a-osx.pkg) |
 | [August 13, 2020](https://storage.googleapis.com/swift-tensorflow-artifacts/macos-toolchains/swift-tensorflow-DEVELOPMENT-2020-08-13-a-osx.pkg) |
 | [August 5, 2020](https://storage.googleapis.com/swift-tensorflow-artifacts/macos-toolchains/swift-tensorflow-DEVELOPMENT-2020-08-05-a-osx.pkg) |