SCons: Add emitter to declutter build objects

SConstruct

@@ -14,6 +14,7 @@ from importlib.util import module_from_spec, spec_from_file_location
 from types import ModuleType
 
 from SCons import __version__ as scons_raw_version
+from SCons.Builder import ListEmitter
 
 # Explicitly resolve the helper modules, this is done to avoid clash with
 # modules of the same name that might be randomly added (e.g. someone adding
@@ -236,6 +237,13 @@ opts.Add(BoolVariable("engine_update_check", "Enable engine update checks in the
 opts.Add(BoolVariable("steamapi", "Enable minimal SteamAPI integration for usage time tracking (editor only)", False))
 opts.Add("cache_path", "Path to a directory where SCons cache files will be stored. No value disables the cache.", "")
 opts.Add("cache_limit", "Max size (in GiB) for the SCons cache. 0 means no limit.", "0")
+opts.Add(
+    BoolVariable(
+        "redirect_build_objects",
+        "Enable redirecting built objects/libraries to `bin/obj/` to declutter the repository.",
+        True,
+    )
+)
 
 # Thirdparty libraries
 opts.Add(BoolVariable("builtin_brotli", "Use the built-in Brotli library", True))
@@ -1052,6 +1060,14 @@ if env["ninja"]:
 if env["threads"]:
     env.Append(CPPDEFINES=["THREADS_ENABLED"])
 
+# Ensure build objects are put in their own folder if `redirect_build_objects` is enabled.
+env.Prepend(LIBEMITTER=[methods.redirect_emitter])
+env.Prepend(SHLIBEMITTER=[methods.redirect_emitter])
+for key in (emitters := env.StaticObject.builder.emitter):
+    emitters[key] = ListEmitter([methods.redirect_emitter] + env.Flatten(emitters[key]))
+for key in (emitters := env.SharedObject.builder.emitter):
+    emitters[key] = ListEmitter([methods.redirect_emitter] + env.Flatten(emitters[key]))
+
 # Build subdirs, the build order is dependent on link order.
 Export("env")