THRIFT-5657: Use Swift 5.7 in travis build (#2719)

diff --git a/build/docker/ubuntu-bionic/Dockerfile b/build/docker/ubuntu-bionic/Dockerfile
index 5d5f7ca..e8f8b24 100644
--- a/build/docker/ubuntu-bionic/Dockerfile
+++ b/build/docker/ubuntu-bionic/Dockerfile
@@ -264,10 +264,13 @@
       libpython-dev \
       libxml2-dev && \
       cd / && \
-      wget --quiet https://swift.org/builds/swift-5.1.4-release/ubuntu1804/swift-5.1.4-RELEASE/swift-5.1.4-RELEASE-ubuntu18.04.tar.gz && \
-      tar xf swift-5.1.4-RELEASE-ubuntu18.04.tar.gz --strip-components=1 && \
-      rm swift-5.1.4-RELEASE-ubuntu18.04.tar.gz && \
-      swift --version
+      wget --quiet https://download.swift.org/swift-5.7-release/ubuntu1804/swift-5.7-RELEASE/swift-5.7-RELEASE-ubuntu18.04.tar.gz && \
+      tar xf swift-5.7-RELEASE-ubuntu18.04.tar.gz && \
+      mv swift-5.7-RELEASE-ubuntu18.04 /usr/share/swift && \
+      rm swift-5.7-RELEASE-ubuntu18.04.tar.gz
+
+ENV PATH /usr/share/swift/usr/bin:$PATH
+RUN swift --version
 
 # Locale(s) for cpp unit tests
 RUN apt-get install -y --no-install-recommends \