Makefile.dev is only included if a Git clone is detected.

make evaluates macros in target specifications when the Makefile is
read, which meant that the build-all-asts target caused `git ls-files`
to be called on every invocation of make. This tweaks it to be a
recursive call to make which puts the $(AST_FILES) macro in the recipe
where it is only evaluated when the target is requested.

(cherry picked from commit 93ee6b43b05783d56e3d8d984fb2503f5870807d)