Run CI using ubuntu-20.04 (#44)

Author: lwronski

.github/workflows/ci.yml

@@ -9,7 +9,7 @@ on:
 
 jobs:
   test:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     strategy:
       fail-fast: false
     steps:
@@ -25,7 +25,7 @@ jobs:
 
   publish:
     needs: test
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     if: github.event_name == 'push'
     steps:
       - uses: actions/checkout@v3
@@ -50,7 +50,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-latest, windows-latest, macos-latest]
+        os: [ubuntu-20.04, windows-latest, macos-latest]
         scalaJsVersion: ["1.9.0", "1.10.0", "1.10.1", "1.11.0", "1.12.0", "1.13.0"]
     steps:
       - uses: actions/checkout@v2
@@ -91,7 +91,7 @@ jobs:
 
   generate-static-launcher:
     needs: test
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     strategy:
       fail-fast: false
       matrix:
@@ -125,7 +125,7 @@ jobs:
 
   generate-mostly-static-launcher:
     needs: test
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     strategy:
       fail-fast: false
       matrix: