Auto merge of #7875 - ehuss:update-jobserver, r=alexcrichton

Update jobserver.

Keep in sync with rust-lang/rust (rust-lang/rust#68663), so that local users and lib users get the same version.

Author: bors

Cargo.toml

@@ -42,7 +42,7 @@ home = "0.5"
 humantime = "2.0.0"
 ignore = "0.4.7"
 lazy_static = "1.2.0"
-jobserver = "0.1.13"
+jobserver = "0.1.21"
 lazycell = "1.2.0"
 libc = "0.2"
 log = "0.4.6"