In general, CentOS 7, released 7 years ago, is not supported by Chromium's build ecosystem. gn's Linux pre-build binaries build on Ubuntu 16.04 (glibc 2.23) , so it's no wonder these binaries won't work on CentOS 7. You have to build gn from source.
Fortunately, gn itself can be built with a C++17 compliant compiler without any other dependencies. See  for details.
You can also take inspiration from the RPM spec of EPEL(Extra Packages for Enterprise Linux) 7. See .
Also, if you have other gn related questions, I recommend discussing them at https://groups.google.com/a/chromium.org/g/gn-dev.