Update ccpp.yml

Temporary: Don't use // build on github (to try to  understand why it doesn't build on Github, whereas it works locally :-<)

.github/workflows/ccpp.yml

@@ -14,7 +14,7 @@ jobs:
     - name: configure
       run: ./configure
     - name: make
-      run: make -j$(nproc)
+      run: make -j1
     - name: make check
       run: make check
 #    - name: make distcheck