Fix issue with Debian xstd compression

We are downgrading Ubuntu to 20.04 which is not using xstd compression
More context in [issue #2376](#2376)

Co-authored-by: Shwetha Gururaj <gururajsh@vmware.com>
Co-authored-by: Alex Rocha <alexr1@vmware.com>

Author: 3 people

.github/workflows/build-sign-upload.yml

@@ -146,7 +146,7 @@ jobs:
     name: Build Linux
     needs:
     - setup
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     environment: ${{ needs.setup.outputs.secrets-environment }}
 
     env:
@@ -991,9 +991,9 @@ jobs:
     - setup
     - build-linux
     environment: ${{ needs.setup.outputs.secrets-environment }}
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     container:
-      image: ubuntu
+      image: ubuntu:20.04
     steps:
 
     - name: Download Signed Linux Packages

.github/workflows/update-repos.yml

@@ -235,7 +235,7 @@ jobs:
 
   update-deb:
     name: Update Debian Repository
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     needs: setup
     environment: ${{ needs.setup.outputs.secrets-environment }}
     env:
@@ -307,7 +307,7 @@ jobs:
 
   test-deb:
     name: Test Debian Repository
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     needs:
     - setup
     - update-deb