Updated GitHub actions to use glibc 2.28 instead of glibc 2.17 for bu…

…ilding the AppImages

   Distro    |  kernel | glibc
     ---     |   ---   |  ---
  CentOS 7   |   3.10  |  2.17
  CentOS 8   |   4.18  |  2.28
  Debian 9   |  4.9.30 |  2.24
  Debian 10  | 4.9.118 |  2.28
  Debian 11  | 5.10.84 |  2.31
   RHEL 7    |   3.10  |  2.17
   RHEL 8    |   4.18  |  2.28
Ubuntu 18.04 |   4.15  |  2.27
Ubuntu 20.04 |   5.4   |  2.31

.github/workflows/cmake-ninja.yml

@@ -13,17 +13,17 @@ jobs:
     # See: https://docs.github.com/en/free-pro-team@latest/actions/learn-github-actions/managing-complex-workflows#using-a-build-matrix
     runs-on: ubuntu-latest
 
-    # Use centos7
+    # Use centos8
     container:
-      image: centos:7
+      image: centos:8
       options: --privileged
 
     steps:
 
     - name: Install GIT
       shell: bash
       run: |
-        yum -y install https://packages.endpointdev.com/rhel/7/os/x86_64/endpoint-repo.x86_64.rpm
+        yum -y install https://packages.endpointdev.com/rhel/8/main/x86_64/endpoint-repo.noarch.rpm
         yum -y install git
         git --version