Use compilers from devtoolset-7 for CentOS 6

Signed-off-by: Balasankar "Balu" C <balasankarc@autistici.org>

.gitlab-ci.yml

@@ -42,7 +42,7 @@ variables:
   # will use images from that registry and not depend on GitLab.com
   BUILDER_IMAGE_REGISTRY: "registry.gitlab.com/gitlab-org/gitlab-omnibus-builder"
   PUBLIC_BUILDER_IMAGE_REGISTRY: "registry.gitlab.com/gitlab-org/gitlab-omnibus-builder"
-  BUILDER_IMAGE_REVISION: "0.0.67"
+  BUILDER_IMAGE_REVISION: "0.0.70"
   # The registry to pull the assets image from
   ASSET_REGISTRY: "${CI_REGISTRY}"
   ASSET_SYNC_EXISTING_REMOTE_FILES: "keep"

changelogs/unreleased/5554-new-cmake.yml

+---
+title: Use new CMake for building libgit2 as part of Gitaly build
+merge_request: 4468
+author:
+type: other

config/software/gitlab-rails.rb

@@ -78,7 +78,7 @@ build do
   block 'use a custom compiler (gcc 6.3 instead of 4.4.7) in CentOS 6' do
     next unless ohai['platform'] == 'centos' && ohai['platform_version'].start_with?('6.')
-    env['PATH'] = "/opt/rh/devtoolset-6/root/usr/bin:#{env['PATH']}"
+    env['PATH'] = "/opt/rh/devtoolset-7/root/usr/bin:#{env['PATH']}"
   end
   bundle_without = %w(development test)