Contrary to some beliefs, the buddha.dll file is an official part of the base Sleeping Dogs game (Steam, GOG, or console versions). It is almost exclusively associated with modded versions of the game, specifically:
Jun snorted. “And you’re installing it.”
Before downloading anything new, check if your antivirus already "captured" the file.
Recommended source: Search for “Sleeping Dogs SweetFX 1.4” on Nexus Mods—the bundle includes a clean buddha.dll.