Try to avoid deleting trees in Cargo's tests

[alexcrichton]

An attempt at rust-lang/rust#48775

[rust-highfive]

r? @matklad

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[alexcrichton]

@bors: r+

[bors]

📌 Commit d856711 has been approved by alexcrichton

[bors]

⌛ Testing commit d856711 with merge 03af18ce262ea477514f19b3562288a31ac784c8...

[bors]

💔 Test failed - status-appveyor

[kennytm]

Oh the irony.

[00:17:50] failures:
[00:17:50] 
[00:17:50] ---- build_script::rename_with_link_search_path stdout ----
[00:17:50] 	running `C:\projects\cargo\target\debug\cargo.exe build`
[00:17:50] running `C:\projects\cargo\target\debug\cargo.exe run`
[00:17:50] thread 'build_script::rename_with_link_search_path' panicked at 'called `Result::unwrap()` on an `Err` value: Os { code: 5, kind: PermissionDenied, message: "Access is denied." }', libcore\result.rs:945:5
[00:17:50] note: Run with `RUST_BACKTRACE=1` for a backtrace.
[00:17:50] 
[00:17:50] 
[00:17:50] failures:
[00:17:50]     build_script::rename_with_link_search_path
[00:17:50] 
[00:17:50] test result: FAILED. 1164 passed; 1 failed; 9 ignored; 0 measured; 0 filtered out

[alexcrichton]

Well I guess that answers that question!

Turns out this was the wrong unwrap anyway, closing.