switch to path dependencies for first party crates

Change-Id: Ic1a912abc99815312f93b1f9386d0745e0662b85
diff --git a/Cargo.toml b/Cargo.toml
index 40ba4e9..b0c417c 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -27,7 +27,7 @@
 futures = "0.1.15"
 
 [target.'cfg(target_os = "fuchsia")'.dependencies]
-fuchsia-zircon = "0.3"
+fuchsia-zircon = { path = "../../garnet/public/rust/crates/fuchsia-zircon" }
 
 [dev-dependencies]
 env_logger = { version = "0.4", default-features = false }