Summary:
On some platforms like MacOS, a second 'make check' can lead to
/bin/rm: Argument list too long

This is fixed by replacing with a 'find'. Also, using '-f' for more rm calls
to avoid prompt.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7095

Test Plan: 'make check' on Linux and MacOS

Reviewed By: riversand963

Differential Revision: D22415808

Pulled By: pdillinger

fbshipit-source-id: 0fd1ebae13739c9d81f9e813e99b062715604d6b