ci: fix no-std check

.github/workflows/ci.yml

@@ -80,13 +80,15 @@ jobs:
     - uses: actions/checkout@master
 
     - name: setup
-      run: rustup target add thumbv7m-none-eabi
+      run: |
+        rustup default nightly
+        rustup target add thumbv7m-none-eabi
 
     - name: check no_std
       uses: actions-rs/cargo@v1
       with:
         command:  check
-        args: --no-default-features --features alloc --target thumbv7m-none-eabi -v
+        args: --no-default-features --features alloc --target thumbv7m-none-eabi -Z avoid-dev-deps
 
   check_fmt_and_docs:
     name: Checking fmt and docs