Test and release on Ubuntu 20.04 for greater GLIBC compatibility

Fixes: #180
Signed-off-by: Juan Cruz Viotti <[email protected]>

Author: jviotti

.github/workflows/package.yml

@@ -20,7 +20,7 @@ jobs:
       fail-fast: false
       matrix:
         platform:
-          - os: ubuntu-latest
+          - os: ubuntu-20.04
             cc: clang
             cxx: clang++
             shell: sh

.github/workflows/test.yml

@@ -9,11 +9,11 @@ jobs:
       fail-fast: false
       matrix:
         platform:
-          - os: ubuntu-latest
+          - os: ubuntu-20.04
             cc: clang
             cxx: clang++
             shell: sh
-          - os: ubuntu-latest
+          - os: ubuntu-20.04
             cc: gcc
             cxx: g++
             shell: sh