coreboot-sdk/Dockerfile: Add 'gettext' and 'xfonts-unifont'

Required for building grub2.

BUG=N/A
TEST=Build successfully for 'QEMU x86 i440fx/piix4' with GRUB2 payload.

Change-Id: I97860f33dd3fde2f6db2f005d65b53cd669403e9
Signed-off-by: Harrie Paijmans <hpaijmans@eltan.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/83676
Reviewed-by: Frans Hendriks <fhendriks@eltan.com>
Reviewed-by: Martin L Roth <gaumless@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

util/docker/coreboot-sdk/Dockerfile

@@ -33,6 +33,7 @@ RUN \
 		g++ \
 		gawk \
 		gcc \
+		gettext \
 		git \
 		gnat \
 		golang \
@@ -86,6 +87,7 @@ RUN \
 		uuid-dev \
 		vim-common \
 		wget \
+		xfonts-unifont \
 		xz-utils \
 		zlib1g-dev \
 	&& apt-get clean