CI: Add test case for disabling MOP FUSION

Add a new test case to the CI pipeline when the MOP FUSION is disabled.
This ensures better coverage and prevents regressions for this specific
configuration.

Author: eleanorLYJ

.github/workflows/main.yml

@@ -81,6 +81,7 @@ jobs:
             make distclean && make ENABLE_EXT_C=0 check -j$(nproc)
             make distclean && make ENABLE_SDL=0 check -j$(nproc)
             make distclean && make ENABLE_Zicsr=0 check -j$(nproc)
+            make distclean && make ENABLE_MOP_FUSION=0 check -j$(nproc)
     - name: misalignment test in block emulation
       env:
         CC: ${{ steps.install_cc.outputs.cc }}