Drop support of CentOS 7

Official support of CentOS 7 ends on 2024-06-30. Also, by default it's shipped with outdated tools: GCC (4.8.5), Make, Autoconf, etc. Some of them may be installed using (https://wiki.centos.org/AdditionalResources/Repositories/SCL). Thus, additional steps are needed for configuring environment for building Linux or toolchains.

May dropping support of CentOS 7 in favor of 8 be considered?