[ci] Produce combined BIOS/UEFI ISO and USB images

Use util/genfsimg to combine the 64-bit BIOS and all UEFI builds into
a single multi-architecture image in both ISO and USB formats.

Include an editable autoexec.ipxe script (that matches the default
iPXE behaviour) in the USB image, so that users can just mount and
edit this file.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

.github/workflows/build.yml

@@ -33,6 +33,7 @@ jobs:
                ${{ env.bindir }}/8086100e.mrom \
                ${{ env.bindir }}/ipxe.dsk \
                ${{ env.bindir }}/ipxe.iso \
+               ${{ env.bindir }}/ipxe.lkrn \
                ${{ env.bindir }}/ipxe.pxe \
                ${{ env.bindir }}/ipxe.usb \
                ${{ env.bindir }}/undionly.kpxe
@@ -43,9 +44,8 @@ jobs:
           name: ${{ env.bindir }}
           if-no-files-found: error
           path: |
-            src/${{ env.bindir }}/ipxe.iso
+            src/${{ env.bindir }}/ipxe.lkrn
             src/${{ env.bindir }}/ipxe.pxe
-            src/${{ env.bindir }}/ipxe.usb
             src/${{ env.bindir }}/undionly.kpxe
 
   sbi:
@@ -120,8 +120,6 @@ jobs:
           if-no-files-found: error
           path: |
             src/${{ env.bindir }}/ipxe.efi
-            src/${{ env.bindir }}/ipxe.iso
-            src/${{ env.bindir }}/ipxe.usb
             src/${{ env.bindir }}/snponly.efi
 
   tests:
@@ -163,3 +161,53 @@ jobs:
         working-directory: src
         run: |
           ${{ matrix.exec }} ${{ env.bindir }}/tests.linux
+
+  combine:
+    name: BIOS + UEFI
+    runs-on: ubuntu-latest
+    needs:
+      - bios
+      - uefi
+    container:
+      image: ghcr.io/ipxe/ipxe-signer
+    env:
+      binaries: >-
+        bin-x86_64-pcbios/ipxe.lkrn
+        bin-arm32-efi/ipxe.efi
+        bin-arm64-efi/ipxe.efi
+        bin-i386-efi/ipxe.efi
+        bin-loong64-efi/ipxe.efi
+        bin-riscv32-efi/ipxe.efi
+        bin-riscv64-efi/ipxe.efi
+        bin-x86_64-efi/ipxe.efi
+    steps:
+
+      - name: Check out code
+        uses: actions/checkout@v6
+
+      - name: Download
+        uses: actions/download-artifact@v7
+        with:
+          pattern: "{bin-x86_64-pcbios,bin-*-efi}"
+
+      - name: Combine
+        run: |
+          # Provide an editable placeholder autoexec.ipxe for the USB image
+          cat > autoexec.ipxe <<'EOF'
+          #!ipxe
+          echo
+          prompt --key 0x02 --timeout 2000 \
+              Press Ctrl-B for the iPXE command line... \
+              && shell || autoboot
+          EOF
+          ./src/util/genfsimg -o ipxe.iso ${{ env.binaries }}
+          ./src/util/genfsimg -o ipxe.usb -s autoexec.ipxe ${{ env.binaries }}
+
+      - name: Upload
+        uses: actions/upload-artifact@v6
+        with:
+          name: bin-combined
+          if-no-files-found: error
+          path: |
+            ipxe.iso
+            ipxe.usb