gummiboot: split *.efi.stub into subpackage

dracut-uefi and mkinitcpio (since upcoming v31) needs UEFI stub from
gummiboot (or systemd, which is the same; systemd has absorbed
gummiboot) to bundle Linux kernel and initramdisk into a UEFI executable
- and only the stub, not gummiboot bootloader itself, nor any hooks.

srcpkgs/gummiboot-efistub

@@ -0,0 +1 @@
+gummiboot

srcpkgs/gummiboot/template

@@ -1,12 +1,13 @@
 # Template file for 'gummiboot'
 pkgname=gummiboot
 version=48.1
-revision=7
+revision=8
 archs="i686* x86_64* aarch64*"
 build_style=gnu-configure
 conf_files="/etc/default/gummiboot"
 hostmakedepends="automake pkg-config libxslt docbook-xsl"
 makedepends="gnu-efi-libs liblzma-devel libblkid-devel"
+depends="${pkgname}-efistub>=${version}_${revision}"
 short_desc="Simple UEFI Boot Manager"
 maintainer="Érico Nogueira <ericonr@disroot.org>"
 license="LGPL-2.0-or-later"
@@ -34,3 +35,11 @@ post_install() {
 	vinstall ${FILESDIR}/kernel.d/gummiboot.confd 644 \
 		etc/default gummiboot
 }
+
+gummiboot-efistub_package() {
+	short_desc="Linux UEFI stub from the gummiboot project"
+
+	pkg_install() {
+		vmove "usr/lib/gummiboot/*.efi.stub"
+	}
+}