fix: add missing flag

Author: 0x416e746f6e

build.sh

@@ -16,6 +16,7 @@ export RUSTFLAGS="\
 
 export CARGO_TARGET_$( echo "${TARGET}" | tr '[:lower:]' '[:upper:]' | tr '-' '_' )_RUSTFLAGS="\
   --cfg tracing_unstable \
+  --cfg tokio_unstable \
   --remap-path-prefix /app=. \
   -C codegen-units=1 \
   -C embed-bitcode=no \