Target dependent on dynamically generated dependency list

[Kip Warner]

Hey list,

I have an XML file that is part of my source tree. It contains a list
of files that are to be compiled into my executable, such as icons,
menus, etc. for GtkBuilder. This happens when glib-compile-resources(1)
tool consumes this XML file and emits C source and header files that
can be compiled into object code (e.g. BUILT_SOURCES), linked with the
resulting executable, and referenced via program logic at run time.

When one of the files referenced in the XML (a GResource file) is
updated the build environment should re-generate the resulting source
code.

The glib-compile-resources(1) tool has a switch that allows it to not
emit any code, but just output a dependency list compatible with most
implementations of Make, e.g. akin to gcc -M.

What is the most elegant and portable way to integrate this
functionality into my Automake Makefile.am? This is my solution so far,
but I really don't think this feels elegant.

https://pastebin.com/STGvw2Fd

Yours truly,