Add s390x support for linuxkit docker images

Add support for s390 architecture for linuxkit/alpine and the
other docker images in tools and pkg.

Signed-off-by: Alice Frosi <alice@linux.vnet.ibm.com>

tools/alpine/packages

@@ -46,7 +46,6 @@ gmp-dev
 gnupg
 go
 grep
-gummiboot
 hvtools
 installkernel
 iperf3
@@ -65,7 +64,6 @@ libressl-dev
 libseccomp-dev
 libtirpc-dev
 libtool
-libunwind-dev
 linux-headers
 lsscsi
 make