ci: deal with CentOS 7 EOL and disappearance of yum mirrors (#1839)

This was breaking CI for us. Hard break for icc/icx tests, since those
REQUIRED a yum install of the intel compilers. Softer undetected break
for all the ASWF <= 2022 containers based on CentOS 7, which were not
failing outright but were failing to install certain optional
packages.

The solution (for now) is to configure yum to exclude the missing repo.

Signed-off-by: Larry Gritz <lg@larrygritz.com>

src/build-scripts/gh-installdeps.bash

@@ -12,12 +12,19 @@ set -ex
 # Install system packages when those are acceptable for dependencies.
 #
 if [[ "$ASWF_ORG" != ""  ]] ; then
-    # Using ASWF CentOS container
+    # Using ASWF container
 
     export PATH=/opt/rh/devtoolset-6/root/usr/bin:/usr/local/bin:$PATH
 
     #ls /etc/yum.repos.d
 
+    if [[ "$ASWF_VFXPLATFORM_VERSION" == "2021" || "$ASWF_VFXPLATFORM_VERSION" == "2022" ]] ; then
+        # CentOS 7 based containers need the now-nonexistant centos repo to be
+        # excluded or all the subsequent yum install commands will fail.
+        yum-config-manager --disable centos-sclo-rh && true
+        sed -i 's,^mirrorlist=,#,; s,^#baseurl=http://mirror\.centos\.org/centos/$releasever,baseurl=https://vault.centos.org/7.9.2009,' /etc/yum.repos.d/CentOS-Base.repo
+    fi
+
     sudo /usr/bin/yum install -y giflib giflib-devel && true
     # sudo /usr/bin/yum install -y ffmpeg ffmpeg-devel && true