add CI step to run rtic-sync loom tests

.github/workflows/build.yml

@@ -265,6 +265,16 @@ jobs:
       - name: Run cargo test
         run: cargo xtask --deny-warnings --backend ${{ matrix.backend }} test ${{ matrix.package }}
 
+  loom-tests:
+    name: rtic-sync loom tests
+    runs-on: ubuntu-22.04
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Run cargo test
+        run: RUSTFLAGS="--cfg loom" cargo test -p rtic-sync --release --lib
+
   # Build documentation, check links
   docs:
     name: build docs
@@ -661,6 +671,7 @@ jobs:
       - check-clippy
       - testexamples
       - tests
+      - loom-tests
       - docs
       - mdbook
     runs-on: ubuntu-22.04