Enable Xcode 12 with fresh SwiftWasm 5.3 snapshot (swiftwasm#35)

* Enable Xcode 12 with fresh SwiftWasm 5.3 snapshot

* Fix snapshot URLs in `test.yml`

Author: MaxDesiatov

.github/workflows/test.yml

@@ -8,9 +8,9 @@ jobs:
         os: [macOS-10.15, Ubuntu-18.04]
         include:
           - os: macOS-10.15
-            toolchain: https://github.com/swiftwasm/swift/releases/download/swift-wasm-DEVELOPMENT-SNAPSHOT-2020-06-12-a/swift-wasm-DEVELOPMENT-SNAPSHOT-2020-06-12-a-osx.tar.gz
+            toolchain: https://github.com/swiftwasm/swift/releases/download/swift-wasm-5.3-SNAPSHOT-2020-08-10-a/swift-wasm-5.3-SNAPSHOT-2020-08-10-a-osx.tar.gz
           - os: Ubuntu-18.04
-            toolchain: https://github.com/swiftwasm/swift/releases/download/swift-wasm-DEVELOPMENT-SNAPSHOT-2020-06-12-a/swift-wasm-DEVELOPMENT-SNAPSHOT-2020-06-12-a-linux.tar.gz
+            toolchain: https://github.com/swiftwasm/swift/releases/download/swift-wasm-5.3-SNAPSHOT-2020-08-10-a/swift-wasm-5.3-SNAPSHOT-2020-08-10-a-linux.tar.gz
     runs-on: ${{ matrix.os }}
     steps:
       - name: Checkout

.swift-version

@@ -1 +1 @@
-wasm-DEVELOPMENT-SNAPSHOT-2020-06-12-a
+wasm-5.3-SNAPSHOT-2020-08-10-a