GHA: Build in an Ubuntu 20.04 runner

.github/workflows/build-linux.yml

@@ -65,7 +65,7 @@ on:
 jobs:
   build-linux:
     name: build
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-20.04
 
     strategy:
       fail-fast: false
@@ -77,6 +77,13 @@ jobs:
      #      suffix: -debug
 
     steps:
+      - name: 'Install some dependencies'
+        run: |
+          apt-get update
+          apt-get install -y build-essential git wget curl sudo unzip zip openjdk-11-jdk autoconf libfreetype6-dev libcups2-dev libx11-dev libxext-dev libxrender-dev libxrandr-dev libxtst-dev libxt-dev libasound2-dev libffi-dev file binutils libfontconfig-dev
+          # If we really need gcc-10, we can get it from this PPA:
+          #sudo add-apt-repository ppa:ubuntu-toolchain-r/test
+
       - name: 'Checkout the JDK source'
         uses: actions/checkout@v4
 
@@ -104,8 +111,10 @@ jobs:
 
       # Upgrading apt to solve libc6 installation bugs, see JDK-8260460.
       - name: 'Install toolchain and dependencies'
+        shell: bash
         run: |
           # Install dependencies using apt-get
+          set -vx
           if [[ '${{ inputs.apt-architecture }}' != '' ]]; then
             sudo dpkg --add-architecture ${{ inputs.apt-architecture }}
           fi

.github/workflows/main.yml

@@ -57,7 +57,7 @@ jobs:
 
   select:
     name: 'Select platforms'
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-20.04
     outputs:
       linux-x64: ${{ steps.include.outputs.linux-x64 }}
       linux-x86: ${{ steps.include.outputs.linux-x86 }}
@@ -300,7 +300,7 @@ jobs:
     with:
       platform: linux-x64
       bootjdk-platform: linux-x64
-      runs-on: ubuntu-22.04
+      runs-on: ubuntu-20.04
 
   test-linux-x86:
     name: linux-x86
@@ -310,7 +310,7 @@ jobs:
     with:
       platform: linux-x86
       bootjdk-platform: linux-x64
-      runs-on: ubuntu-22.04
+      runs-on: ubuntu-20.04
 
   test-macos-x64:
     name: macos-x64
@@ -335,7 +335,7 @@ jobs:
   # Remove bundles so they are not misconstrued as binary distributions from the JDK project
   remove-bundles:
     name: 'Remove bundle artifacts'
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-20.04
     if: always()
     needs:
       - build-linux-x64