use vendored Rust crates

Summary: Actually use vendored Rust crates when building with CMake. The `--offline` option make sure cargo do not go to the Internet for missing crates.

Reviewed By: simpkins

Differential Revision: D20542672

fbshipit-source-id: ab4af40150c6af8b531a75f503a4fa848b3914da

build/fbcode_builder/manifests/eden

@@ -56,3 +56,6 @@ fbcode/tools/lfs = tools/lfs
 
 [cmake.defines.all(fb=on,os=windows)]
 INSTALL_PYTHON_LIB=ON
+
+[cmake.defines.fb=on]
+USE_CARGO_VENDOR=ON