Split SYSLINUX configuration into per-kernel configuration files

Slightly simplifies adding boot loader configuration for more kernels.
Unfortunately the INCLUDE statement doesn't support wildcards, so each new file must be manually included in the main syslinux configuration file (syslinux.cfg for baseline and archiso_sys.cfg for releng).

configs/baseline/syslinux/syslinux-linux.cfg

+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+LABEL arch
+MENU LABEL Arch Linux
+LINUX boot/%ARCH%/vmlinuz-linux
+INITRD boot/%ARCH%/initramfs-linux.img
+APPEND archisobasedir=%INSTALL_DIR% archisolabel=%ARCHISO_LABEL%

configs/baseline/syslinux/syslinux.cfg

@@ -8,8 +8,4 @@ MENU CLEAR
 DEFAULT arch
 TIMEOUT 30
 
-LABEL arch
-MENU LABEL Arch Linux
-LINUX boot/%ARCH%/vmlinuz-linux
-INITRD boot/%ARCH%/initramfs-linux.img
-APPEND archisobasedir=%INSTALL_DIR% archisolabel=%ARCHISO_LABEL%
+INCLUDE boot/syslinux/syslinux-linux.cfg

configs/releng/syslinux/archiso_pxe-linux.cfg

+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+LABEL arch64_nbd
+TEXT HELP
+Boot the Arch Linux install medium using NBD.
+It allows you to install Arch Linux or perform system maintenance.
+ENDTEXT
+MENU LABEL Arch Linux install medium (x86_64, NBD)
+LINUX boot/x86_64/vmlinuz-linux
+INITRD boot/intel-ucode.img,boot/amd-ucode.img,boot/x86_64/initramfs-linux.img
+APPEND archisobasedir=%INSTALL_DIR% archisolabel=%ARCHISO_LABEL% archiso_nbd_srv=${pxeserver} checksum verify
+SYSAPPEND 3
+
+LABEL arch64_nfs
+TEXT HELP
+Boot the Arch Linux live medium using NFS.
+It allows you to install Arch Linux or perform system maintenance.
+ENDTEXT
+MENU LABEL Arch Linux install medium (x86_64, NFS)
+LINUX boot/x86_64/vmlinuz-linux
+INITRD boot/intel-ucode.img,boot/amd-ucode.img,boot/x86_64/initramfs-linux.img
+APPEND archisobasedir=%INSTALL_DIR% archiso_nfs_srv=${pxeserver}:/run/archiso/bootmnt checksum verify
+SYSAPPEND 3
+
+LABEL arch64_http
+TEXT HELP
+Boot the Arch Linux live medium using HTTP.
+It allows you to install Arch Linux or perform system maintenance.
+ENDTEXT
+MENU LABEL Arch Linux install medium (x86_64, HTTP)
+LINUX boot/x86_64/vmlinuz-linux
+INITRD boot/intel-ucode.img,boot/amd-ucode.img,boot/x86_64/initramfs-linux.img
+APPEND archisobasedir=%INSTALL_DIR% archiso_http_srv=http://${pxeserver}/ checksum verify
+SYSAPPEND 3

configs/releng/syslinux/archiso_pxe.cfg

@@ -3,37 +3,6 @@
 
 INCLUDE boot/syslinux/archiso_head.cfg
 
-LABEL arch64_nbd
-TEXT HELP
-Boot the Arch Linux install medium using NBD.
-It allows you to install Arch Linux or perform system maintenance.
-ENDTEXT
-MENU LABEL Arch Linux install medium (x86_64, NBD)
-LINUX boot/x86_64/vmlinuz-linux
-INITRD boot/intel-ucode.img,boot/amd-ucode.img,boot/x86_64/initramfs-linux.img
-APPEND archisobasedir=%INSTALL_DIR% archisolabel=%ARCHISO_LABEL% archiso_nbd_srv=${pxeserver} checksum verify
-SYSAPPEND 3
-
-LABEL arch64_nfs
-TEXT HELP
-Boot the Arch Linux live medium using NFS.
-It allows you to install Arch Linux or perform system maintenance.
-ENDTEXT
-MENU LABEL Arch Linux install medium (x86_64, NFS)
-LINUX boot/x86_64/vmlinuz-linux
-INITRD boot/intel-ucode.img,boot/amd-ucode.img,boot/x86_64/initramfs-linux.img
-APPEND archisobasedir=%INSTALL_DIR% archiso_nfs_srv=${pxeserver}:/run/archiso/bootmnt checksum verify
-SYSAPPEND 3
-
-LABEL arch64_http
-TEXT HELP
-Boot the Arch Linux live medium using HTTP.
-It allows you to install Arch Linux or perform system maintenance.
-ENDTEXT
-MENU LABEL Arch Linux install medium (x86_64, HTTP)
-LINUX boot/x86_64/vmlinuz-linux
-INITRD boot/intel-ucode.img,boot/amd-ucode.img,boot/x86_64/initramfs-linux.img
-APPEND archisobasedir=%INSTALL_DIR% archiso_http_srv=http://${pxeserver}/ checksum verify
-SYSAPPEND 3
+INCLUDE boot/syslinux/archiso_pxe-linux.cfg
 
 INCLUDE boot/syslinux/archiso_tail.cfg

configs/releng/syslinux/archiso_sys-linux.cfg

+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+LABEL arch64
+TEXT HELP
+Boot the Arch Linux install medium on BIOS.
+It allows you to install Arch Linux or perform system maintenance.
+ENDTEXT
+MENU LABEL Arch Linux install medium (x86_64, BIOS)
+LINUX boot/x86_64/vmlinuz-linux
+INITRD boot/intel-ucode.img,boot/amd-ucode.img,boot/x86_64/initramfs-linux.img
+APPEND archisobasedir=%INSTALL_DIR% archisolabel=%ARCHISO_LABEL%

configs/releng/syslinux/archiso_sys.cfg

@@ -6,14 +6,6 @@ INCLUDE boot/syslinux/archiso_head.cfg
 DEFAULT arch64
 TIMEOUT 30
 
-LABEL arch64
-TEXT HELP
-Boot the Arch Linux install medium on BIOS.
-It allows you to install Arch Linux or perform system maintenance.
-ENDTEXT
-MENU LABEL Arch Linux install medium (x86_64, BIOS)
-LINUX boot/x86_64/vmlinuz-linux
-INITRD boot/intel-ucode.img,boot/amd-ucode.img,boot/x86_64/initramfs-linux.img
-APPEND archisobasedir=%INSTALL_DIR% archisolabel=%ARCHISO_LABEL%
+INCLUDE boot/syslinux/archiso_sys-linux.cfg
 
 INCLUDE boot/syslinux/archiso_tail.cfg