[CI] Upload nightly builds to S3 (#4976)

* Do not store built artifacts in the Jenkins master

* Add wheel renaming script

* Upload wheels to S3 bucket

* Use env.GIT_COMMIT

* Capture git hash correctly

* Add missing import in Jenkinsfile

* Address reviewer's comments

* Put artifacts for pull requests in separate directory

* No wildcard expansion in Windows CMD

Jenkinsfile-win64

@@ -3,6 +3,11 @@
 
 /* Jenkins pipeline for Windows AMD64 target */
 
+import groovy.transform.Field
+
+@Field
+def commit_id   // necessary to pass a variable from one stage to another
+
 pipeline {
   agent none
   // Build stages
@@ -12,6 +17,7 @@ pipeline {
       steps {
         script {
           checkoutSrcs()
+          commit_id = "${GIT_COMMIT}"
         }
         stash name: 'srcs'
         milestone ordinal: 1
@@ -76,7 +82,7 @@ def BuildWin64() {
     """
     bat """
     cd python-package
-    conda activate && python setup.py bdist_wheel --universal
+    conda activate && python setup.py bdist_wheel --universal && for /R %%i in (dist\\*.whl) DO python ../tests/ci_build/rename_whl.py "%%i" ${commit_id} win_amd64
     """
     echo "Insert vcomp140.dll (OpenMP runtime) into the wheel..."
     bat """
@@ -86,7 +92,8 @@ def BuildWin64() {
     """
     echo 'Stashing Python wheel...'
     stash name: 'xgboost_whl', includes: 'python-package/dist/*.whl'
-    archiveArtifacts artifacts: "python-package/dist/*.whl", allowEmptyArchive: true
+    path = ("${BRANCH_NAME}" == 'master') ? '/' : "${BRANCH_NAME}/"
+    s3Upload bucket: 'xgboost-nightly-builds', path: path, acl: 'PublicRead', workingDir: 'python-package/dist', includePathPattern:'**/*.whl'
     echo 'Stashing C++ test executable (testxgboost)...'
     stash name: 'xgboost_cpp_tests', includes: 'build/testxgboost.exe'
     deleteDir()