Cargo is not excluding target/ directories from MacOS time machine

[orf]

Problem
Seems to be the same as #7189. Cargo no longer marks target/, or any subdirectories, as excluded from time machine backups. This causes lots of backup bloat!

Steps

1. Run cargo new my-cool-project
2. Run cargo build my-cool-project
3. Run tmutil isexcluded target/ and see that it says the target/ directory is included in backups.

Possible Solution(s)
The current implementation seems too fragile, as it's broken before and it's broken now. Simply setting the com.apple.metadata:com_apple_backup_excludeItem xattr on the directory is enough, rather than invoking an Objective-C framework method.

Notes

Output of cargo version: cargo 1.37.0 (9edd089 2019-08-02)

Latest MacOS.

[orf]

CC @alexcrichton - sorry for the notification, but I saw you worked on this in #7189.

[ehuss]

It was fixed in 1.38, did you try that version?

[orf]

I feel so stupid, I'm sorry. I thought that it was fixed in 1.37. Confirmed it works as expected in 1.38.0.