[build] Create util/gensrvimg for building network boot server images

In the spirit of util/genfsimg, create a script util/gensrvimg that
can be used to install compiled iPXE binaries to a directory tree
suitable for copying to a TFTP or HTTP server.

The script detects the CPU architecture for each input file and
installs it into the appropriate subdirectory.  Top-level symlinks are
created for each filename, with earlier files taking precedence.

Signed binaries are detected and automatically placed into a Secure
Boot specific subdirectory, thereby allowing the reduced-feature
Secure Boot binaries to coexist with full-feature binaries in a single
installation directory tree.  An iPXE shim may be specified and will
be automatically installed alongside the signed binaries, with the
relevant symlink created for each signed binary.

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

.github/workflows/build.yml

@@ -360,7 +360,7 @@ jobs:
             shimx64.efi
 
   combine:
-    name: BIOS + UEFI
+    name: Combine
     runs-on: ubuntu-latest
     needs:
       - bios
@@ -370,7 +370,10 @@ jobs:
     container:
       image: ghcr.io/ipxe/ipxe-builder-utils
     env:
-      binaries: >-
+      efishims: >-
+        -e shim/shimaa64.efi
+        -e shim/shimx64.efi
+      fsbinaries: >-
         bin-x86_64-pcbios/${DRIVERS}.lkrn
         bin-arm32-efi/${DRIVERS}.efi
         bin-arm64-efi/${DRIVERS}.efi
@@ -379,6 +382,38 @@ jobs:
         bin-riscv32-efi/${DRIVERS}.efi
         bin-riscv64-efi/${DRIVERS}.efi
         bin-x86_64-efi/${DRIVERS}.efi
+      srvbinaries: >-
+        bin/ipxe.pxe
+        bin/ipxe-legacy.pxe
+        bin/undionly.kpxe
+        bin-arm32-efi/ipxe.efi
+        bin-arm32-efi/ipxe-legacy.efi
+        bin-arm32-efi/snponly.efi
+        bin-arm64-efi/ipxe.efi
+        bin-arm64-efi/ipxe-legacy.efi
+        bin-arm64-efi/snponly.efi
+        bin-arm64-efi-sb/ipxe.efi
+        bin-arm64-efi-sb/snponly.efi
+        bin-i386-efi/ipxe.efi
+        bin-i386-efi/ipxe-legacy.efi
+        bin-i386-efi/snponly.efi
+        bin-loong64-efi/ipxe.efi
+        bin-loong64-efi/ipxe-legacy.efi
+        bin-loong64-efi/snponly.efi
+        bin-riscv32-efi/ipxe.efi
+        bin-riscv32-efi/ipxe-legacy.efi
+        bin-riscv32-efi/snponly.efi
+        bin-riscv64-efi/ipxe.efi
+        bin-riscv64-efi/ipxe-legacy.efi
+        bin-riscv64-efi/snponly.efi
+        bin-x86_64-efi/ipxe.efi
+        bin-x86_64-efi/ipxe-legacy.efi
+        bin-x86_64-efi/snponly.efi
+        bin-x86_64-efi-sb/ipxe.efi
+        bin-x86_64-efi-sb/snponly.efi
+        bin-x86_64-pcbios/ipxe.pxe
+        bin-x86_64-pcbios/ipxe-legacy.pxe
+        bin-x86_64-pcbios/undionly.kpxe
     steps:
 
       - name: Check out code
@@ -387,9 +422,9 @@ jobs:
       - name: Download
         uses: actions/download-artifact@v7
         with:
-          pattern: "{bin-x86_64-pcbios,bin-*-efi,bin-*-efi-sb,shim}"
+          pattern: "{bin,bin-x86_64-pcbios,bin-*-efi,bin-*-efi-sb,shim}"
 
-      - name: Combine
+      - name: ISO + USB
         run: |
           # Provide an editable placeholder autoexec.ipxe for the USB image
           cat > autoexec.ipxe <<'EOF'
@@ -400,11 +435,16 @@ jobs:
               && shell || autoboot
           EOF
           for DRIVERS in ipxe ipxe-legacy ; do
-              ./src/util/genfsimg -o ${DRIVERS}.iso ${{ env.binaries }}
+              ./src/util/genfsimg -o ${DRIVERS}.iso ${{ env.fsbinaries }}
               ./src/util/genfsimg -o ${DRIVERS}.usb -s autoexec.ipxe \
-                                  ${{ env.binaries }}
+                                  ${{ env.fsbinaries }}
           done
 
+      - name: Server
+        run: |
+          ./src/util/gensrvimg -o ipxeboot.tar.gz ${{ env.efishims }} \
+              ${{ env.srvbinaries }}
+
       - name: Upload
         uses: actions/upload-artifact@v6
         with:
@@ -415,6 +455,7 @@ jobs:
             ipxe.usb
             ipxe-legacy.iso
             ipxe-legacy.usb
+            ipxeboot.tar.gz
 
   netboot:
     name: Netboot