convertor: option to disable sparse file

[WaberZhuang]

What this PR does / why we need it:
Sparse files may not work well in some environments, so just in case we add an option to not use sparse file during converting.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

Please check the following list:

• Does the affected code have corresponding tests, e.g. unit test, E2E test?
• Does this change require a documentation update?
• Does this introduce breaking changes that would require an announcement or bumping the major version?
• Do all new files have an appropriate license header?

[yuchen0cc]

LGTM