Delete file hierarchies.
Deleting file hierarchies may be slow. This clears a given path by moving it to a trash directory which can be deleted at the end of the build asynchronously.
val create : B00_std.Fpath.t -> tcreate dir is a trash using directory dir for data storage. dir may not exist.
val dir : t -> B00_std.Fpath.tdir t is the trash's directory (may not exist)
val trash : t -> B00_std.Fpath.t -> (unit, string) resulttrash t p trashes path p in dir t. If p does not exist this has no effect. Note that p needs to be on the same device as dir t and that the latter is created if needed.
delete ~block t deletes t's trash directory and its content. If block is true the operation is synchronous and blocks until the trash is effectively deleted; if false the operation is spawn as a separate process.
Note. On Windows block:false relies on cmd.exe being available.