Add Swift 5.3 testing for more platforms

.gitlab/ci/amazonlinux-2.yml

@@ -5,6 +5,10 @@ swift trunk:
   image: swiftlang/swift:nightly-master-amazonlinux2
   allow_failure: true
 
+swift 5.3:
+  extends: .unit-test
+  image: swiftlang/swift:nightly-5.3-amazonlinux2
+
 swift 5.2:
   extends: .unit-test
   image: swift:5.2-amazonlinux2

.gitlab/ci/centos-8.yml

@@ -5,6 +5,10 @@ swift trunk:
   image: swiftlang/swift:nightly-master-centos8
   allow_failure: true
 
+swift 5.3:
+  extends: .unit-test
+  image: swiftlang/swift:nightly-5.3-centos8
+
 swift 5.2:
   extends: .unit-test
   image: swift:5.2-centos8

.gitlab/ci/ubuntu-focal.yml

@@ -5,6 +5,10 @@ swift trunk:
   image: swiftlang/swift:nightly-master-focal
   allow_failure: true
 
+swift 5.3:
+  extends: .unit-test
+  image: swiftlang/swift:nightly-5.3-focal
+
 swift 5.2:
   extends: .unit-test
   image: swift:5.2-focal