CI: Add test case for disabling MOP_FUSION with JIT enabled

Add a new test case to the CI pipeline to verify JIT functionality when
the MOP_FUSION extension is disabled. This ensures better coverage and
prevents regressions for this specific configuration.

Author: eleanorLYJ

.github/workflows/main.yml

@@ -120,6 +120,7 @@ jobs:
             make ENABLE_JIT=1 clean && make ENABLE_Zbs=0 ENABLE_JIT=1 check -j$(nproc)
             make ENABLE_JIT=1 clean && make ENABLE_Zicsr=0 ENABLE_JIT=1 check -j$(nproc)
             make ENABLE_JIT=1 clean && make ENABLE_Zifencei=0 ENABLE_JIT=1 check -j$(nproc)
+            make ENABLE_JIT=1 clean && make ENABLE_MOP_FUSION=0 ENABLE_JIT=1 check -j$(nproc)
     - name: undefined behavior test
       run: |
             make clean && make ENABLE_UBSAN=1 check -j$(nproc)