[rust][3p] Expose crossbeam-channel as unversioned dep.

Want to use this in Starnix without having to add
all of crossbeam to our build times.

Change-Id: I9d70eaaaaecbf464fd2d43305c190ca08ac536d8
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1193315
Commit-Queue: Auto-Submit <[email protected]>
Fuchsia-Auto-Submit: Adam Perry <[email protected]>
Reviewed-by: Erick Tryzelaar <[email protected]>

Author: anp

third_party/rust_crates/BUILD.gn

@@ -189,6 +189,10 @@ group("crossbeam") {
   public_deps = [ ":crossbeam-v0_8_0" ]
 }
 
+group("crossbeam-channel") {
+  public_deps = [ ":crossbeam-channel-v0_5_1" ]
+}
+
 group("crossbeam-utils") {
   public_deps = [ ":crossbeam-utils-v0_8_14" ]
 }
@@ -3776,6 +3780,7 @@ rust_library("crossbeam-channel-v0_5_1") {
     "-Cmetadata=4f2cca7fb0f4b481",
     "-Cextra-filename=-4f2cca7fb0f4b481",
     "--cfg=feature=\"crossbeam-utils\"",
+    "--cfg=feature=\"default\"",
     "--cfg=feature=\"std\"",
   ]
 

third_party/rust_crates/Cargo.lock

@@ -79,6 +79,7 @@ clap = "2.34"
 crc = "1.8.1"
 criterion = { version = "0.2", default-features = false }
 crossbeam = "0.8.0"
+crossbeam-channel = "0.5.1"
 crossbeam-utils = "0.8.14"
 csv = "1.2.1"
 darling = "0.20.10"