Follow redirects for ktlint download (#3543)

The github release page is redirecting, so follow the redirects. 

Good news, the uploading is working and the cipd package is created: https://chrome-infra-packages.appspot.com/p/flutter/ktlint/linux-amd64

Bad news, the uploaded ktlint file is empty because the curl is failing because we aren't following the redirect. 

Passing the `-L` to curl fixes this (I double checked that with `-L` passed locally, we download a working version of ktlint). Sorry, should have caught this in the original PR.

cipd_packages/ktlint/tools/build.sh

@@ -18,4 +18,4 @@ KTLINT_FILE_NAME=$(cat $DIR/../ktlint_metadata.txt | cut -d ',' -f 2)
 # Create the package structure.
 rm -rf $DIR/../build && mkdir -p $DIR/../build
 
-curl https://github.com/pinterest/ktlint/releases/download/"$KTLINT_MAJOR_VERSION"/"$KTLINT_FILE_NAME" -o $DIR/../build/ktlint
+curl -L https://github.com/pinterest/ktlint/releases/download/"$KTLINT_MAJOR_VERSION"/"$KTLINT_FILE_NAME" -o $DIR/../build/ktlint