travis: put cache-control header for ziglang.org/download

Author: andrewrk

ci/travis_linux_script

@@ -19,5 +19,5 @@ if [ "${TRAVIS_PULL_REQUEST}" = "false" ]; then
   echo "secret_key = $AWS_SECRET_ACCESS_KEY" >> ~/.s3cfg
   s3cmd put -P $TRAVIS_BUILD_DIR/artifacts/* s3://ziglang.org/builds/
   touch empty
-  s3cmd put -P empty s3://ziglang.org/builds/zig-linux-x86_64-$TRAVIS_BRANCH.tar.xz --add-header=x-amz-website-redirect-location:/builds/$(ls $TRAVIS_BUILD_DIR/artifacts)
+  s3cmd put -P empty s3://ziglang.org/builds/zig-linux-x86_64-$TRAVIS_BRANCH.tar.xz --add-header="Cache-Control: max-age=0, must-revalidate" --add-header=x-amz-website-redirect-location:/builds/$(ls $TRAVIS_BUILD_DIR/artifacts)
 fi