Fix typo

Author: Joseph-Edwards

.github/workflows/tests.yml

@@ -52,7 +52,7 @@ jobs:
         run: pip install -r requirements.txt
       - name: "Pip install libsemigroups_pybind11 . . ."
         run: |
-          CXX="${{ matrix.compiler }}" LDFLAGS pip install . -v
+          CXX="${{ matrix.compiler }}" pip install . -v
       - name: "Run tests . . ."
         run: |
           python -m pytest -vv tests/test_*.py