Add arm-to-x86 cross-compile matrix and generalize apt setup

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: hsbt

.github/workflows/crosscompile.yml

@@ -22,17 +22,26 @@ permissions:
 
 jobs:
   make:
+    name: make (${{ matrix.host }} host on ${{ matrix.build }})
     strategy:
       matrix:
         include:
           - host: aarch64-linux-gnu
             arch: arm64
+            build: x86_64-linux-gnu
+            runs-on: ubuntu-24.04
+            file_arch: ARM aarch64
+          - host: x86_64-linux-gnu
+            arch: amd64
+            build: aarch64-linux-gnu
+            runs-on: ubuntu-24.04-arm
+            file_arch: x86-64
       fail-fast: false
 
     env:
       GITPULLOPTIONS: --no-tags origin ${{ github.ref }}
 
-    runs-on: ubuntu-24.04
+    runs-on: ${{ matrix.runs-on }}
 
     if: >-
       ${{!(false
@@ -58,17 +67,23 @@ jobs:
       - name: Install cross-compilation toolchain
         run: |
           sudo dpkg --add-architecture ${{ matrix.arch }}
-          # Restrict existing sources to amd64to avoid 404 on arm64
+          native_arch=$(dpkg --print-architecture)
+          # Restrict existing sources to native arch
           sudo sed -i '/^Architectures:/d' /etc/apt/sources.list.d/ubuntu.sources
-          sudo sed -i '/^Types:/a Architectures: amd64 i386' /etc/apt/sources.list.d/ubuntu.sources
-          # Add arm64 sources from ports.ubuntu.com
+          sudo sed -i "/^Types:/a Architectures: ${native_arch}" /etc/apt/sources.list.d/ubuntu.sources
+          # Add cross-arch sources
+          if [ "${{ matrix.arch }}" = "arm64" ]; then
+            cross_uri="http://ports.ubuntu.com/"
+          else
+            cross_uri="http://archive.ubuntu.com/ubuntu/"
+          fi
           printf '%s\n' \
             "Types: deb" \
-            "URIs: http://ports.ubuntu.com/" \
+            "URIs: ${cross_uri}" \
             "Suites: noble noble-updates noble-security" \
             "Components: main universe" \
             "Architectures: ${{ matrix.arch }}" \
-            | sudo tee /etc/apt/sources.list.d/ports-${{ matrix.arch }}.sources
+            | sudo tee /etc/apt/sources.list.d/cross-${{ matrix.arch }}.sources
           sudo apt-get update -qq
           sudo apt-get install --no-install-recommends -qq -y \
             crossbuild-essential-${{ matrix.arch }} \
@@ -92,7 +107,7 @@ jobs:
         run: >-
           ../src/configure -C --disable-install-doc
           --prefix=/usr
-          --build=x86_64-linux-gnu
+          --build=${{ matrix.build }}
           --host=${{ matrix.host }}
           --with-baseruby=$PWD/../baseruby/install/bin/ruby
 
@@ -103,7 +118,7 @@ jobs:
       - name: Verify cross-compiled binary
         run: |
           file install/usr/bin/ruby
-          file install/usr/bin/ruby | grep -q '${{ matrix.host }}\|aarch64'
+          file install/usr/bin/ruby | grep -q '${{ matrix.file_arch }}'
 
       - uses: ./.github/actions/slack
         with: