This looks like cmake is configured to use the system wide C and C++ compilers. The Arduino should be using the one that got downloaded to ${HOME}/.platformio. Also, I’m wondering why cmake is even being used, none of my Uno/Duemilanove/Nano/NormDuino boards use it – they use avr-g++.
I also see “codeblocks” in the above. I imagine that you would need to add the avr-gcc/avr-g++ compilers as a “kit” in CodeBlocks to be able to compile for the Arduino.
How exactly did you create the new project? I use
pio init --board uno --ide codeblocks
When I need to use CodeBlocks as my IDE.
Cheers,
Norm.