linux: add support for ZSTD compression

Add support for creating self-extractible kernels compressed with ZSTD.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

linux/Config.in

@@ -321,6 +321,9 @@ config BR2_LINUX_KERNEL_LZO
 config BR2_LINUX_KERNEL_XZ
 	bool "xz compression"
 
+config BR2_LINUX_KERNEL_ZSTD
+	bool "zstd compression"
+
 endchoice
 
 config BR2_LINUX_KERNEL_IMAGE_TARGET_NAME

linux/linux.mk

@@ -98,12 +98,15 @@ else ifeq ($(BR2_LINUX_KERNEL_LZO),y)
 LINUX_DEPENDENCIES += host-lzop
 else ifeq ($(BR2_LINUX_KERNEL_XZ),y)
 LINUX_DEPENDENCIES += host-xz
+else ifeq ($(BR2_LINUX_KERNEL_ZSTD),y)
+LINUX_DEPENDENCIES += host-zstd
 endif
 LINUX_COMPRESSION_OPT_$(BR2_LINUX_KERNEL_GZIP) += CONFIG_KERNEL_GZIP
 LINUX_COMPRESSION_OPT_$(BR2_LINUX_KERNEL_LZ4) += CONFIG_KERNEL_LZ4
 LINUX_COMPRESSION_OPT_$(BR2_LINUX_KERNEL_LZMA) += CONFIG_KERNEL_LZMA
 LINUX_COMPRESSION_OPT_$(BR2_LINUX_KERNEL_LZO) += CONFIG_KERNEL_LZO
 LINUX_COMPRESSION_OPT_$(BR2_LINUX_KERNEL_XZ) += CONFIG_KERNEL_XZ
+LINUX_COMPRESSION_OPT_$(BR2_LINUX_KERNEL_ZSTD) += CONFIG_KERNEL_ZSTD
 
 ifeq ($(BR2_LINUX_KERNEL_NEEDS_HOST_OPENSSL),y)
 LINUX_DEPENDENCIES += host-openssl