CI: update Ubuntu image to 20.04

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 08299af372f2097fb38c20841ae97380fc2a0c5f..85bd2923b2f73994685f784bbe74049a02c653aa 100644 (file)
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -43,7 +43,7 @@ jobs:
         path: libarchive.tar.xz
 
   Ubuntu:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     strategy:
       matrix:
         bs: [autotools, cmake]
@@ -83,7 +83,7 @@ jobs:
         name: libarchive-ubuntu-${{ matrix.bs }}-${{ matrix.crypto }}-${{ github.sha }}
         path: libarchive.tar.xz
   Ubuntu-distcheck:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
     - uses: actions/checkout@master
     - name: Install dependencies