Hello,
Overkill indeed.
This is how to set the -fcommon flag properly:
-fcommon
Or, if command lines suit you: cmake (...) -DCMAKE_CXX_FLAGS=-fcommon -DCMAKE_C_FLAGS=-fcommon.
cmake (...) -DCMAKE_CXX_FLAGS=-fcommon -DCMAKE_C_FLAGS=-fcommon
regards,
Paulo