meson: Prepare to accept per-binary TargetInfo structure implementation

If a file defining the binary TargetInfo structure is available,
link with it. Otherwise keep using the stub.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Acked-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20251021205741.57109-6-philmd@linaro.org>

configs/targets/meson.build

@@ -0,0 +1,4 @@
+foreach target : [
+  ]
+  config_target_info += {target : files(target + '.c')}
+endforeach