The easiest way to do that would be to right-click on the project in Solution Explorer and select VisualGDB Project Properties. Then go to the Makefile Settings page and edit the CFLAGS via GUI. VisualGDB will automatically update the related Makefiles and reconfigure IntelliSense.
Please note that if you are using MSBuild, you would need to use the VS Project Properties instead.
I have set these flags -mcpu=cortex-a8 -mfloat-abi=hard -mfpu=neon -H in CMake project settings in CFLAG and CXXFLAGS fields, but I got the same error as I do not believe that the compiler ‘sees’ these flags.
Is there a way to see what flags are applied when the compiler is trying to produce the .o file and the executable ?