Bug 1484437: Add cbindgen to the searchfox jobs. r=froydnj

Otherwise they'll fail to build. This is a very similar patch to the one for
bug 1480392.

Differential Revision: https://phabricator.services.mozilla.com/D3690

taskcluster/ci/searchfox/kind.yml

@@ -48,6 +48,7 @@ jobs:
             - linux64-clang
             - linux64-node
             - linux64-rust
+            - linux64-cbindgen
 
     macosx64-searchfox/debug:
         description: "MacOS X x64 Debug Cross-compile Searchfox"
@@ -80,6 +81,7 @@ jobs:
             - linux64-llvm-dsymutil
             - linux64-node
             - linux64-rust-macos
+            - linux64-cbindgen
 
     # NOTE: Windows Searchfox jobs aren't working quite yet (bug 1418415).
 
@@ -109,3 +111,4 @@ jobs:
             - win64-clang-cl
             - win64-node
             - win64-rust
+            - win64-cbindgen