datastructures: replace `lazy_static` by `SyncLazy` from std

Cargo.lock

@@ -3417,7 +3417,6 @@ dependencies = [
  "ena",
  "indexmap",
  "jobserver",
- "lazy_static",
  "libc",
  "measureme",
  "parking_lot 0.10.2",

compiler/rustc_data_structures/Cargo.toml

@@ -12,7 +12,6 @@ ena = "0.14"
 indexmap = "1.5.1"
 tracing = "0.1"
 jobserver_crate = { version = "0.1.13", package = "jobserver" }
-lazy_static = "1"
 rustc_serialize = { path = "../rustc_serialize" }
 rustc_macros = { path = "../rustc_macros" }
 rustc_graphviz = { path = "../rustc_graphviz" }

compiler/rustc_data_structures/src/jobserver.rs

@@ -1,33 +1,31 @@
 pub use jobserver_crate::Client;
-use lazy_static::lazy_static;
+use std::lazy::SyncLazy;
 
-lazy_static! {
-    // We can only call `from_env` once per process
+// We can only call `from_env` once per process
 
-    // Note that this is unsafe because it may misinterpret file descriptors
-    // on Unix as jobserver file descriptors. We hopefully execute this near
-    // the beginning of the process though to ensure we don't get false
-    // positives, or in other words we try to execute this before we open
-    // any file descriptors ourselves.
-    //
-    // Pick a "reasonable maximum" if we don't otherwise have
-    // a jobserver in our environment, capping out at 32 so we
-    // don't take everything down by hogging the process run queue.
-    // The fixed number is used to have deterministic compilation
-    // across machines.
-    //
-    // Also note that we stick this in a global because there could be
-    // multiple rustc instances in this process, and the jobserver is
-    // per-process.
-    static ref GLOBAL_CLIENT: Client = unsafe {
-        Client::from_env().unwrap_or_else(|| {
-            let client = Client::new(32).expect("failed to create jobserver");
-            // Acquire a token for the main thread which we can release later
-            client.acquire_raw().ok();
-            client
-        })
-    };
-}
+// Note that this is unsafe because it may misinterpret file descriptors
+// on Unix as jobserver file descriptors. We hopefully execute this near
+// the beginning of the process though to ensure we don't get false
+// positives, or in other words we try to execute this before we open
+// any file descriptors ourselves.
+//
+// Pick a "reasonable maximum" if we don't otherwise have
+// a jobserver in our environment, capping out at 32 so we
+// don't take everything down by hogging the process run queue.
+// The fixed number is used to have deterministic compilation
+// across machines.
+//
+// Also note that we stick this in a global because there could be
+// multiple rustc instances in this process, and the jobserver is
+// per-process.
+static GLOBAL_CLIENT: SyncLazy<Client> = SyncLazy::new(|| unsafe {
+    Client::from_env().unwrap_or_else(|| {
+        let client = Client::new(32).expect("failed to create jobserver");
+        // Acquire a token for the main thread which we can release later
+        client.acquire_raw().ok();
+        client
+    })
+});
 
 pub fn client() -> Client {
     GLOBAL_CLIENT.clone()