chroot: error out on --network != host when $BUILDAH_ISOLATION

Error out if someone tries to mix the --network CLI flag, with a value
other than "host", with chroot isolation configured by setting
$BUILDAH_ISOLATION to "chroot", as we have been doing for cases where
it's done using the "--isolation" option, instead of just ignoring it as
we did previously.

Signed-off-by: Nalin Dahyabhai <nalin@redhat.com>

Author: nalind

pkg/cli/build.go

@@ -331,7 +331,7 @@ func GenBuildOptions(c *cobra.Command, inputArgs []string, iopts BuildOptions) (
 		}
 	}
 
-	if c.Flag("network").Changed && c.Flag("isolation").Changed {
+	if c.Flag("network").Changed {
 		if isolation == define.IsolationChroot {
 			if ns := namespaceOptions.Find(string(specs.NetworkNamespace)); ns != nil {
 				if !ns.Host {

tests/bud.bats

@@ -569,6 +569,9 @@ _EOF
 
   run_buildah 125 build --network=none --isolation=chroot $WITH_POLICY_JSON ${TEST_SCRATCH_DIR}
   expect_output --substring "cannot set --network other than host with --isolation chroot"
+
+  BUILDAH_ISOLATION=chroot run_buildah 125 build --network=none $WITH_POLICY_JSON ${TEST_SCRATCH_DIR}
+  expect_output --substring "cannot set --network other than host with --isolation chroot"
 }
 
 @test "bud with .dockerignore #1" {