Compiling, linux debian, Arduino IDE 2.1.1
...
Detecting libraries used...
riscv64-unknown-elf-g++: error trying to exec 'cc1plus': execvp: No such file or directory
solved
chmod +x ~/.arduino15/packages/bouffalo/tools/riscv64-unknown-elf/0.0.1/libexec/gcc/riscv64-unknown-elf/8.3.0/cc1plus