Update c-cpp.yml

Add `autoreconf -ivf` step before `./configure`, as `configure` may not be generated yet.

.github/workflows/c-cpp.yml

@@ -13,6 +13,8 @@ jobs:
 
     steps:
     - uses: actions/checkout@v2
+    - name: preconf
+      run: autoreconf -ivf
     - name: configure
       run: ./configure
     - name: make