meson: fix sdbus++ program for subprojects

When sdbusplus is used from the meson-subprojects, the sdbus++ program
is not in the path.  Instead, the subproject emits a variable to find
the location of the tool.  Use that variable to successfully build.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I58c3d240a8a2c39884556e0c71c77811444add4f
diff --git a/xyz/openbmc_project/Dump/Internal/Create/meson.build b/xyz/openbmc_project/Dump/Internal/Create/meson.build
index 52294fa..fd25ad9 100644
--- a/xyz/openbmc_project/Dump/Internal/Create/meson.build
+++ b/xyz/openbmc_project/Dump/Internal/Create/meson.build
@@ -1,11 +1,9 @@
 # SPDX-License-Identifier: Apache-2.0
 
-sdbuscpp = find_program('sdbus++')
-
 server_hpp = custom_target(
                 'server.hpp',
                 command : [
-                    sdbuscpp, '-r', meson.source_root(),
+                    sdbusplusplus_prog, '-r', meson.source_root(),
                     'interface',
                     'server-header',
                     'xyz.openbmc_project.Dump.Internal.Create',
@@ -20,7 +18,7 @@
 server_cpp = custom_target(
                 'server.cpp',
                 command : [
-                    sdbuscpp, '-r', meson.source_root(),
+                    sdbusplusplus_prog, '-r', meson.source_root(),
                     'interface',
                     'server-cpp',
                     'xyz.openbmc_project.Dump.Internal.Create'