ci: add dependent crate

there is an issue reported in comments of rs-ipfs#458 that it happens on any
dependent crate, without any code. hoping that this will work as a test
case so that we wont introduce such again.

.github/workflows/ci.yml

@@ -120,6 +120,11 @@ jobs:
       if: matrix.platform.cross == false
       run: cargo build --locked --workspace --all-targets
 
+    - name: Check dependent crate
+      if: matrix.platform.cross == false # TODO: unsure if this would matter
+      run: cargo check
+      working-directory: test_dependent_crate
+
     - name: Run interop DHT tests with go-ipfs
       if: matrix.platform.host == 'ubuntu-latest' && matrix.platform.cross == false
       run: cargo test --features=test_go_interop dht

test_dependent_crate/.gitignore

@@ -0,0 +1,2 @@
+Cargo.lock
+target/

test_dependent_crate/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "test_dependent_crate"
+version = "0.1.0"
+edition = "2018"
+description = "Crate plays the part of external dependent crate, see #458"
+
+[dependencies]
+ipfs = { path = "../" }
+
+# Prevent this from interfering with workspaces
+[workspace]
+members = ["."]

test_dependent_crate/src/main.rs

@@ -0,0 +1,3 @@
+fn main() {
+    println!("It doesn't matter what's here; this crate is meant to be just `cargo check`'d");
+}