ext: lib: mgmt: mcumgr: Build support for mcumgr.

Adds the necessary CMakeLists.txt and Kconfig files to build the
external mcumgr library.

Signed-off-by: Christopher Collins <ccollins@apache.org>

ext/Kconfig

@@ -14,6 +14,8 @@ source "ext/lib/crypto/Kconfig"
 
 source "ext/lib/encoding/Kconfig"
 
+source "ext/lib/mgmt/Kconfig"
+
 source "ext/debug/Kconfig"
 
 endmenu

ext/lib/CMakeLists.txt

@@ -1,2 +1,3 @@
 add_subdirectory(crypto)
 add_subdirectory(encoding)
+add_subdirectory(mgmt)

ext/lib/mgmt/Kconfig

@@ -0,0 +1,24 @@
+#
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#  http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+#
+
+menu "Management"
+
+source "ext/lib/mgmt/mcumgr/Kconfig"
+
+endmenu

ext/lib/mgmt/mcumgr/Kconfig

@@ -15,7 +15,7 @@
 # specific language governing permissions and limitations
 # under the License.
 
-menuconfig MCUMGR
+config MCUMGR
     bool
     prompt "mcumgr Support"
     select TINYCBOR