ci: split distro-qemu into build-initramfs + run-qemu jobs

Split the monolithic build-and-run.sh into two scripts:
- build-initramfs.sh: builds test binaries, downloads parcagpu,
  creates debootstrap rootfs, and packs the initramfs (once per arch)
- run-qemu.sh: boots a kernel with the pre-built initramfs in QEMU

In CI, a new build-distro-qemu-initramfs job runs once per arch on
native runners (no cross-compilation needed), uploads the initramfs
as an artifact, and the per-kernel distro-qemu-tests jobs download it.

This eliminates redundant Go compilation, debootstrap, and parcagpu
downloads across 10 amd64 + 4 arm64 kernel matrix entries. The run
jobs now only need QEMU installed.

build-and-run.sh remains as a thin wrapper for local development.

Tested locally: build-initramfs.sh + run-qemu.sh pass on 6.6.31.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: gnurizen

.github/workflows/unit-test-on-pull-request.yml

@@ -225,10 +225,54 @@ jobs:
           uname -a
           sudo go test ./interpreter/... -v -run "TestIntegration/(node-local-nightly|node-latest)"
 
+  build-distro-qemu-initramfs:
+    name: Build distro QEMU initramfs (${{ matrix.target_arch }})
+    runs-on: ${{ matrix.runner }}
+    timeout-minutes: 10
+    strategy:
+      matrix:
+        include:
+          - { target_arch: amd64, runner: ubuntu-24.04 }
+          - { target_arch: arm64, runner: ubuntu-24.04-arm }
+    steps:
+      - name: Clone code
+        uses: actions/checkout@v4
+      - name: Set up Go
+        uses: actions/setup-go@v5
+        with:
+          go-version-file: go.mod
+          cache-dependency-path: go.sum
+      - name: Set up environment
+        uses: ./.github/workflows/env
+      - name: Install dependencies
+        run: |
+          sudo apt-get update -y
+          sudo apt-get install -y --no-install-recommends debootstrap systemtap-sdt-dev
+      - name: Get parcagpu image digest
+        id: parcagpu-digest
+        run: |
+          digest=$(docker buildx imagetools inspect ghcr.io/parca-dev/parcagpu:latest --format '{{.Digest}}' 2>/dev/null || echo "unknown")
+          echo "digest=${digest}" >> "$GITHUB_OUTPUT"
+      - name: Cache parcagpu library
+        uses: actions/cache@0400d5f644dc74513175e3cd8d07132dd4860809 # v4.2.4
+        with:
+          path: test/distro-qemu/parcagpu-lib
+          key: parcagpu-${{ matrix.target_arch }}-${{ steps.parcagpu-digest.outputs.digest }}
+      - name: Build initramfs
+        run: |
+          cd test/distro-qemu
+          ./build-initramfs.sh initramfs-${{ matrix.target_arch }}.gz
+      - name: Upload initramfs
+        uses: actions/upload-artifact@bbbca2ddaa5d8feaa63e36b76fdaad77386f024f # v7.0.0
+        with:
+          name: distro-qemu-initramfs-${{ matrix.target_arch }}
+          path: test/distro-qemu/initramfs-${{ matrix.target_arch }}.gz
+
   distro-qemu-tests:
     name: Distro QEMU tests (${{ matrix.kernel }} ${{ matrix.target_arch }})
     runs-on: ${{ matrix.target_arch == 'arm64' && 'ubuntu-24.04-arm' || 'ubuntu-24.04' }}
-    timeout-minutes: 15
+    needs: build-distro-qemu-initramfs
+    timeout-minutes: 10
     strategy:
       matrix:
         include:
@@ -253,65 +297,24 @@ jobs:
     steps:
       - name: Clone code
         uses: actions/checkout@v4
-      - name: Set up Go
-        uses: actions/setup-go@v5
-        with:
-          go-version-file: go.mod
-          cache-dependency-path: go.sum
-      - name: Set up environment
-        uses: ./.github/workflows/env
       - name: Install dependencies
         run: |
-          sudo tee /etc/apt/sources.list.d/ubuntu.sources <<EOF > /dev/null
-          Types: deb
-          URIs: http://azure.archive.ubuntu.com/ubuntu/
-          Suites: noble noble-updates noble-backports
-          Components: main universe restricted multiverse
-          Signed-By: /usr/share/keyrings/ubuntu-archive-keyring.gpg
-          Architectures: amd64
-
-          Types: deb
-          URIs: http://azure.ports.ubuntu.com/ubuntu-ports/
-          Suites: noble noble-updates noble-backports
-          Components: main universe restricted multiverse
-          Signed-By: /usr/share/keyrings/ubuntu-archive-keyring.gpg
-          Architectures: arm64
-          EOF
-
-          sudo dpkg --add-architecture arm64
-
           sudo apt-get update -y
           case "${{ matrix.target_arch }}" in
             amd64) sudo apt-get -y --no-install-recommends --no-install-suggests install qemu-system-x86;;
-            arm64) sudo apt-get -y install qemu-system-arm ipxe-qemu gcc-aarch64-linux-gnu libc6-arm64-cross libc6:arm64 binutils-aarch64-linux-gnu musl-dev:arm64;;
+            arm64) sudo apt-get -y --no-install-recommends --no-install-suggests install qemu-system-arm ipxe-qemu;;
             *) echo >&2 "bug: bad arch selected"; exit 1;;
           esac
-          sudo apt-get install -y --no-install-recommends debootstrap
-      - name: Get parcagpu image digest
-        id: parcagpu-digest
-        run: |
-          digest=$(docker buildx imagetools inspect ghcr.io/parca-dev/parcagpu:latest --format '{{.Digest}}' 2>/dev/null || echo "unknown")
-          echo "digest=${digest}" >> "$GITHUB_OUTPUT"
-      - name: Cache parcagpu library
-        uses: actions/cache@0400d5f644dc74513175e3cd8d07132dd4860809 # v4.2.4
+      - name: Fetch initramfs
+        uses: actions/download-artifact@70fc10c6e5e1ce46ad2ea6f2b72d43f7d47b13c3 # v8.0.0
         with:
-          path: test/distro-qemu/parcagpu-lib
-          key: parcagpu-${{ matrix.target_arch }}-${{ steps.parcagpu-digest.outputs.digest }}
+          name: distro-qemu-initramfs-${{ matrix.target_arch }}
+          path: test/distro-qemu
       - name: Download kernel
         run: |
           cd test/distro-qemu
-          case "${{ matrix.target_arch }}" in
-            amd64) export QEMU_ARCH=x86_64;;
-            arm64) export QEMU_ARCH=aarch64;;
-            *) echo >&2 "bug: bad arch selected"; exit 1;;
-          esac
           ./download-kernel.sh ${{ matrix.kernel }}
-      - name: Run Full Distro tests in QEMU
+      - name: Run distro tests in QEMU
         run: |
           cd test/distro-qemu
-          case "${{ matrix.target_arch }}" in
-            amd64) export QEMU_ARCH=x86_64;;
-            arm64) export QEMU_ARCH=aarch64;;
-            *) echo >&2 "bug: bad arch selected"; exit 1;;
-          esac
-          ./build-and-run.sh ${{ matrix.kernel }}
+          ./run-qemu.sh ${{ matrix.kernel }} initramfs-${{ matrix.target_arch }}.gz