Work around lru-disk-cache UB in Rust 1.48

Summary: `lru-disk-cache` depends on an old version of `linked-hash-map` which contains UB in 1.48 (see mozilla/sccache#813). They updated the deps in their repo months ago, but haven't pushed a new version. This diff makes us get `lru-disk-cache` directly from their GitHub instead.

Reviewed By: dtolnay

Differential Revision: D25134582

fbshipit-source-id: 05fd63a76b7095ebeea458645b92a83bbd8c4614

Cargo.toml

@@ -56,6 +56,7 @@ chashmap = { git = "https://gitlab.redox-os.org/ahornby/chashmap", rev = "901ace
 const-random = { git = "https://github.com/fbsource/const-random", rev = "374c5b46427fe2ffbf6acbd9c1687e0f1a809f95" }
 gotham = { git = "https://github.com/krallin/gotham.git", branch = "socket_data" }
 gotham_derive = { git = "https://github.com/krallin/gotham.git", branch = "socket_data" }
+lru-disk-cache = { git = "https://github.com/mozilla/sccache", rev = "033ebaae69beeb0ac04e8c35d6ff1103487bd9a3" }
 prost = { git = "https://github.com/gabrielrussoc/prost", branch = "protoc-runtime" }
 prost-build = { git = "https://github.com/gabrielrussoc/prost", branch = "protoc-runtime" }
 prost-derive = { git = "https://github.com/gabrielrussoc/prost", branch = "protoc-runtime" }