If setting CFLAGS to cmake from command-line does not work
What happens if you really try to add some CFLAGS to cmake from command-line…
export CFLAGS="-Werror"
export CXXFLAGS="-Werror"
cmake ..
make VERBOSE=1
…but it does not do anything at all?
If you encounter this problem, it is likely that you overwrite CFLAGS somewehere in your CMakeLists.txt files.
For example, replace this:
set(CMAKE_C_FLAGS "-std=c99")
…with the correct one that appends the new flags instead of overwriting them:
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -std=c99")