Add libz-sys to rustc-workspace-hack.

alexcrichton/curl-rust#351 changed
curl-rust to no longer enable the default features of libz-sys.
Because rustfmt includes rustc-workspace-hack with the
rustc-workspace-hack/all-static feature (sometimes), it ends up building
libz-sys without the default features. This causes a duplicate
with other packages (like rls) which enable the default
features.

Cargo.lock

@@ -3435,6 +3435,7 @@ dependencies = [
  "byteorder",
  "crossbeam-utils 0.7.2",
  "libc",
+ "libz-sys",
  "proc-macro2",
  "quote",
  "serde",

src/tools/rustc-workspace-hack/Cargo.toml

@@ -65,6 +65,8 @@ byteorder = { version = "1", features = ['default', 'std'] }
 curl-sys = { version = "0.4.13", features = ["http2", "libnghttp2-sys"], optional = true }
 crossbeam-utils = { version = "0.7.2", features = ["nightly"] }
 libc = { version = "0.2.79", features = ["align"] }
+# Ensure default features of libz-sys, which are disabled in some scenarios.
+libz-sys = { version = "1.1.2" }
 proc-macro2 = { version = "1", features = ["default"] }
 quote = { version = "1", features = ["default"] }
 serde = { version = "1.0.82", features = ['derive'] }