Set ubuntu version to 18.04 to use an older glib version

Author: chippmann

.github/workflows/build.yml

@@ -12,7 +12,7 @@ jobs:
   build:
     strategy:
       matrix:
-        os: [ macOS-latest, windows-latest, ubuntu-latest ]
+        os: [ macOS-latest, windows-latest, ubuntu-18.04 ]
     runs-on: ${{matrix.os}}
     steps:
       - name: Checkout the repo

.github/workflows/deploy.yml

@@ -12,7 +12,7 @@ jobs:
   build:
     strategy:
       matrix:
-        os: [ macOS-latest, windows-latest, ubuntu-latest ]
+        os: [ macOS-latest, windows-latest, ubuntu-18.04 ]
     runs-on: ${{matrix.os}}
     steps:
       - name: Checkout the repo