Specify LD_LIBRARY_PATH in local build

Author: Joseph-Edwards

.github/workflows/tests.yml

@@ -98,6 +98,7 @@ jobs:
       - name: "Set environment variables . . ."
         run: |
           echo "PKG_CONFIG_PATH=$MAMBA_ROOT_PREFIX/envs/libsemigroups/lib/pkgconfig:$MAMBA_ROOT_PREFIX/envs/libsemigroups/share/pkgconfig:/usr/local/lib/pkgconfig" >> $GITHUB_ENV
+          echo "LD_LIBRARY_PATH=$MAMBA_ROOT_PREFIX/envs/libsemigroups/lib:/usr/local/lib"
           echo "PATH=$MAMBA_ROOT_PREFIX/envs/libsemigroups/bin:$PATH" >> $GITHUB_ENV
       - name: "Check Python version . . ."
         run: |