zstd support

[532910]

please add support for zstd or other compressors

[paulmenzel]

As Debian ships XZ compressed modules now, tiny-initramfs fails to load these modules:

[    2.248116] Invalid ELF header magic: != ELF
initramfs: Couldn't load /crc32c-intel.ko.xz: Ex[    2.249299] Invalid ELF header magic: != ELF
ec format error
initramfs: Coul[    2.250618] Invalid ELF header magic: != ELF
dn't load /crc32c_generic.ko.xz:[    2.251905] Invalid ELF header magic: != ELF
 Exec format error
initramfs: Couldn't load /jb[    2.253604] Invalid ELF header magic: != ELF
d2.ko.xz: Exec format error
ini[    2.255050] Invalid ELF header magic: != ELF
tramfs: Couldn't load /mbcache.k[    2.256200] Invalid ELF header magic: != ELF
o.xz: Exec format error
initram[    2.257487] Invalid ELF header magic: != ELF
fs: Couldn't load /crc16.ko.xz: [    2.258784] Invalid ELF header magic: != ELF
Exec format error
initramfs: Co[    2.260059] Invalid ELF header magic: != ELF
uldn't load /ext4.ko.xz: Exec fo[    2.261347] Invalid ELF header magic: != ELF
rmat error
initramfs: Couldn't [    2.262631] Invalid ELF header magic: != ELF
load /virtio_blk.ko.xz: Exec for[    2.263921] Invalid ELF header magic: != ELF
mat error
initramfs: Couldn't l[    2.265238] Invalid ELF header magic: != ELF
oad /crct10dif_common.ko.xz: Exe[    2.266478] Invalid ELF header magic: != ELF
c format error
initramfs: Could[    2.267774] Invalid ELF header magic: != ELF
n't load /crc64.ko.xz: Exec form[    2.269097] Invalid ELF header magic: != ELF
at error
initramfs: Couldn't lo[    2.270347] Invalid ELF header magic: != ELF
ad /crct10dif-pclmul.ko.xz: Exec format error
initramfs: Couldn't load /crct10dif_generic.ko.xz: Exec format error
initramfs: Couldn't load /crc-t10dif.ko.xz: Exec format error
initramfs: Couldn't load /scsi_common.ko.xz: Exec format error
initramfs: Couldn't load /scsi_mod.ko.xz: Exec format error
initramfs: Couldn't load /crc64-rocksoft.ko.xz: Exec format error
initramfs: Couldn't load /t10-pi.ko.xz: Exec format error
initramfs: Couldn't load /sd_mod.ko.xz: Exec format error
initramfs: Couldn't load /virtio_mmio.ko.xz: Exec format error

[viccie30]

I've posted a patch for that on the Debian BTS in the meantime. If there's no response in another few days, I want do a NMU.

The minimal patch is here: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1063142#10