add base_arch variable for future non-x86 work

This variable will allow to select which target architecture has to be
used.

Partially-Implements: blueprint multiarch-and-arm64-containers

Change-Id: I71ddb7ef57c64d2505cac96724b1ab6772a57d6a

kolla/common/config.py

@@ -19,6 +19,7 @@ from kolla.version import version_info as version
 
 
 BASE_OS_DISTRO = ['centos', 'rhel', 'ubuntu', 'oraclelinux', 'debian']
+BASE_ARCH = ['x86_64']
 DISTRO_RELEASE = {
     'centos': '7',
     'rhel': '7',
@@ -154,6 +155,9 @@ _CLI_OPTS = [
                help='The base distro image tag'),
     cfg.StrOpt('base-image',
                help='The base image name. Default is the same with base'),
+    cfg.StrOpt('base-arch', default='x86_64',
+               choices=BASE_ARCH,
+               help='The base architecture.'),
     cfg.BoolOpt('debug', short='d', default=False,
                 help='Turn on debugging log level'),
     cfg.DictOpt('build-args',

kolla/image/build.py

@@ -530,6 +530,7 @@ class KollaWorker(object):
         self.base_tag = conf.base_tag
         self.install_type = conf.install_type
         self.tag = conf.tag
+        self.base_arch = conf.base_arch
         self.images = list()
         rpm_setup_config = ([repo_file for repo_file in
                              conf.rpm_setup_config if repo_file is not None])
@@ -699,6 +700,7 @@ class KollaWorker(object):
             values = {'base_distro': self.base,
                       'base_image': self.conf.base_image,
                       'base_distro_tag': self.base_tag,
+                      'base_arch': self.base_arch,
                       'supported_distro_release': supported_distro_release,
                       'install_metatype': self.install_metatype,
                       'image_prefix': self.image_prefix,

releasenotes/notes/non-x86-support-bce168d78db50202.yaml

@@ -0,0 +1,4 @@
+---
+features:
+  - New CLI argument "--base-arch" allows to select which architecture is
+    targetted by build.