lorax: Add --rootfs-size

This controls how big the root filesystem is for the squashfs used in
the boot.iso, the default is 2GiB.

Note that larger rootfs sizes will require more memory and may cause the
build to fail.

(cherry picked from commit 37d36daa9c)

Resolves: rhbz#1715116

src/sbin/lorax

@@ -189,6 +189,8 @@ def main(args):
             default=[])
     optional.add_option("--noverifyssl", action="store_true", default=False,
                         help="Do not verify SSL certificates")
+    optional.add_option("--rootfs-size", type=int, default=2,
+                        help="Size of root filesystem in GiB. Defaults to 2.")
 
     # dracut arguments
     dracut_group = OptionGroup(parser, "dracut arguments")
@@ -293,6 +295,7 @@ def main(args):
               workdir=tempdir, outputdir=outputdir, buildarch=opts.buildarch,
               volid=opts.volid, domacboot=opts.domacboot, doupgrade=opts.doupgrade,
               installpkgs=opts.installpkgs,
+              size=opts.rootfs_size,
               add_templates=opts.add_templates,
               add_template_vars=parsed_add_template_vars,
               add_arch_templates=opts.add_arch_templates,