sdbus++-gen-meson: create tool for helping with meson

The previous attempt at a meson-helper tool (sdbus++-gendir) had
some usability issues integrating with meson that was not agreeable
to other developers.  The two main complaints were that it did not
automatically catch changes to YAML files and it re-ran the processing
on every YAML file.

The new direction is to create this helper tool which will generate a
tree of meson.build files that can be checked in directly to a
repository and updated whenever a YAML file is added (or removed).

This tool will both create the tree of meson.build necessary for
generating all C++/header and markdown files.  The meson targets created
by the tool also contain callbacks into this tool to abstract details on
which / how sdbus++ is called to generate the output files.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I410ad2121274b2ba9e6f14985bc7b6a2c92e65e7
diff --git a/tools/meson.build b/tools/meson.build
index e9d3a63..bf5d574 100644
--- a/tools/meson.build
+++ b/tools/meson.build
@@ -1,2 +1,3 @@
 sdbusplusplus_prog = find_program('sdbus++')
 sdbusgen_prog = find_program('sdbus++-gendir')
+sdbuspp_gen_meson_prog = find_program('sdbus++-gen-meson')