gha: Add rootfs-initrd-mariner build target

This adds the Mariner guest image build target to the list of assets
as preparation for #6839.

Signed-off-by: Aurélien Bombo <abombo@microsoft.com>

.github/workflows/build-kata-static-tarball-amd64.yaml

@@ -40,6 +40,7 @@ jobs:
           - rootfs-image
           - rootfs-image-tdx
           - rootfs-initrd
+          - rootfs-initrd-mariner
           - rootfs-initrd-sev
           - shim-v2
           - tdvf

tools/packaging/kata-deploy/local-build/Makefile

@@ -43,6 +43,7 @@ serial-targets:
 	${MAKE} -f $(MK_PATH) -j 1 V= \
 	rootfs-image-tarball \
 	rootfs-image-tdx-tarball \
+	rootfs-initrd-mariner-tarball \
 	rootfs-initrd-sev-tarball \
 	rootfs-initrd-tarball \
 	cloud-hypervisor-tarball \
@@ -108,6 +109,9 @@ rootfs-image-tarball:
 rootfs-image-tdx-tarball: kernel-tdx-experimental-tarball
 	${MAKE} $@-build
 
+rootfs-initrd-mariner-tarball:
+	exit 0
+
 rootfs-initrd-sev-tarball: kernel-sev-tarball
 	${MAKE} $@-build