oniro-image: switch image compression from bz2 to gz

This makes is faster to build images, easier to handle them, e.g.
Raspberry Pi imager transparently supports .gz but not .bz2 and makes
virtually no difference to the size of the image.

Remember that the actual image is already compressed, as it is stored
inside the filesystem as a squashfs object.

Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@huawei.com>

meta-oniro-core/classes/oniro-image.bbclass

@@ -31,15 +31,16 @@ IMAGE_FEATURES:append = " read-only-rootfs"
 IMAGE_FSTYPES:append = " squashfs"
 
 WKS_FILE:raspberrypi4-64 ?= "x-raspberrypi.wks.in"
+IMAGE_FSTYPES:raspberrypi4-64 ?= "wic.gz wic.bmap"
 
 WKS_FILE:seco-intel-b68 ?= "x-gpt-efi-disk.wks.in"
-IMAGE_FSTYPES:append:seco-intel-b68 = " wic.bz2 wic.bmap"
+IMAGE_FSTYPES:seco-intel-b68 ?= "wic.gz wic.bmap"
 
 # We avoid any other fstypes (for qemu) by default as the OS depends on a
 # specific partition table provided through the wic configuration.
-IMAGE_FSTYPES:qemux86 ?= "wic wic.bz2"
+IMAGE_FSTYPES:qemux86 ?= "wic wic.gz"
 WKS_FILE:qemux86 ?= "x-gpt-efi-disk.wks.in"
-IMAGE_FSTYPES:qemux86-64 ?= "wic wic.bz2"
+IMAGE_FSTYPES:qemux86-64 ?= "wic wic.gz"
 WKS_FILE:qemux86-64 ?= "x-gpt-efi-disk.wks.in"
 # Build EFI firmware for x86{,-64} QEMU machine.
 WKS_FILE_DEPENDS:qemux86-64 += "ovmf"
@@ -49,7 +50,10 @@ WKS_FILE:qemu-generic-arm64 = "x-qemu-efi-disk.wks.in"
 IMAGE_FSTYPES:qemu-generic-arm64 += "wic wic.qcow2"
 
 WKS_FILE:seco-imx8mm-c61-2gb ?= "x-imx-uboot-bootpart.wks.in"
+IMAGE_FSTYPES:seco-imx8mm-c61-2gb ?= "wic.gz wic.bmap"
+
 WKS_FILE:seco-imx8mm-c61-4gb ?= "x-imx-uboot-bootpart.wks.in"
+IMAGE_FSTYPES:seco-imx8mm-c61-4gb ?= "wic.gz wic.bmap"
 
 #
 # Deploy boot partition artifacts to the root partition. This is part of the