[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

tests/ci_build/rename_whl.py

@@ -0,0 +1,37 @@
+import sys
+import os
+from contextlib import contextmanager
+
+@contextmanager
+def cd(path):
+    path = os.path.normpath(path)
+    cwd = os.getcwd()
+    os.chdir(path)
+    print("cd " + path)
+    try:
+        yield path
+    finally:
+        os.chdir(cwd)
+
+if len(sys.argv) != 4:
+    print('Usage: {} [wheel to rename] [commit id] [platform tag]'.format(sys.argv[0]))
+    sys.exit(1)
+
+whl_path = sys.argv[1]
+commit_id = sys.argv[2]
+platform_tag = sys.argv[3]
+
+assert platform_tag in ['manylinux1_x86_64', 'win_amd64']
+
+dirname, basename = os.path.dirname(whl_path), os.path.basename(whl_path)
+
+with cd(dirname):
+    tokens = basename.split('-')
+    assert len(tokens) == 5
+    keywords = {'pkg_name': tokens[0],
+                'version': tokens[1],
+                'commit_id': commit_id,
+                'platform_tag': platform_tag}
+    new_name = '{pkg_name}-{version}+{commit_id}-py2.py3-none-{platform_tag}.whl'.format(**keywords)
+    print('Renaming {} to {}...'.format(basename, new_name))
+    os.rename(basename, new_name)