Build update_manager.cpp by default

The update_manager is used to determine if the new code update API
should be used.

Tested: Verified the existing interfaces still worked.

Change-Id: I2f00e3c996966bc904eb68b09acbd197421dc6a4
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>
diff --git a/meson.build b/meson.build
index e4808d0..b81d4bf 100644
--- a/meson.build
+++ b/meson.build
@@ -160,7 +160,8 @@
     'serialize.cpp',
     'version.cpp',
     'utils.cpp',
-    'msl_verify.cpp'
+    'msl_verify.cpp',
+    'update_manager.cpp'
 )
 
 if get_option('bmc-layout').contains('static')
@@ -253,10 +254,6 @@
 )
 
 if get_option('software-update-dbus-interface').allowed()
-    image_updater_sources += files(
-        'update_manager.cpp'
-    )
-
     executable(
         'phosphor-software-manager',
         'software_manager.cpp',