How can i resolve this error when installing ROOT

First, uninstall your current binary:

cd cmake-3.14.0-rc2
sudo make uninstall

Then, download and install a CMake.org binary distribution (for the “Linux x86_64” platform).
Either the “Latest Release (3.20.3)”:

wget https://github.com/Kitware/CMake/releases/download/v3.20.3/cmake-3.20.3-linux-x86_64.sh
sudo bash cmake-3.20.3-linux-x86_64.sh --prefix=/usr/local --exclude-subdir

or the “Previous Release (3.19.8)”:

wget https://github.com/Kitware/CMake/releases/download/v3.19.8/cmake-3.19.8-Linux-x86_64.sh
sudo bash cmake-3.19.8-Linux-x86_64.sh --prefix=/usr/local --exclude-subdir

Actually, on Ubuntu, instead of manually installing it, you can use (future updates will then be installed automatically): Kitware’s Ubuntu packages