Merge "Removing unused rustc-1.57.0" am: 394a8fccce am: 532a71f33d am: 539e673a7f

Original change: https://android-review.googlesource.com/c/platform/prebuilts/rust/+/2006590

Change-Id: I628cee209a9d653bbee9c6e2d1604c2381139c8e