rootfs: Add xz as a dep

As we'll be untarring the agent tarball (and any other component that
may be part of the rootfs) into the rootfs, we have to have xz
installed.

For debian and ubuntu the package is called xz-utils; for centos,
alpine and cbl-mariner the package is called xz.

Signed-off-by: Fabiano Fidêncio <fabiano.fidencio@intel.com>

tools/osbuilder/rootfs-builder/alpine/Dockerfile.in

@@ -25,6 +25,7 @@ RUN apk update && apk add --no-cache \
     musl \
     musl-dev \
     protoc \
-    tar
+    tar \
+    xz
 # aarch64 requires this name -- link for all
 RUN ln -s /usr/bin/gcc "/usr/bin/$(uname -m)-linux-musl-gcc"