unsupported GNU version! gcc versions later than 7 are not supported!
unsupported GNU version! gcc versions later than 8 are not supported!

This error is a bother but easy to resolve

1. Install an older version

2. Set it to main binary.

3. Re-run your previous installers that had failed because of the version error.

Users on Ubuntu 19.10 and CentOS 7

Run this in terminal.

bash <(curl -s https://gitlab.com/Shinobi-Systems/supplements/-/blob/master/downgradeGccG++.sh)

This script will install version 7 of GCC and G++ and set them to the main binaries.

More Information about this technique

If you look at the script you'll notice it's fairly simple to change it to another version. Just change the 7 to another number.

You can go ahead and fork the repository, make your changes and run the script from Gitlab in a similar fashion as shown above.

if [ -x "$(command -v apt)" ]; then
    sudo apt-get install gcc-7 g++-7 -y
    rm /usr/bin/gcc
    rm /usr/bin/g++

    ln -s /usr/bin/gcc-7 /usr/bin/gcc
    ln -s /usr/bin/g++-7 /usr/bin/g++
# Check if Cent OS
if [ -x "$(command -v yum)" ]; then
    yum install centos-release-scl
    yum install devtoolset-7-gcc-c++