SCons: Add explicit dependencies on thirdparty code in cloned env

Since we clone the environments to build thirdparty code, we don't get an
explicit dependency on the build objects produced by that environment.

So when we update thirdparty code, Godot code using it is not necessarily
rebuilt (I think it is for changed headers, but not for changed .c/.cpp files),
which can lead to an invalid compilation output (linking old Godot .o files
with a newer, potentially ABI breaking version of thirdparty code).

This was only seen as really problematic with bullet updates (leading to
crashes when rebuilding Godot after a bullet update without cleaning .o files),
but it's safer to fix it everywhere, even if it's a LOT of hacky boilerplate.

3 files changed, 41 insertions, 19 deletions

diff --git a/scene/SCsub b/scene/SCsub
index f9fc00f3f2..ccd2bab8ff 100644
--- a/scene/SCsub
+++ b/scene/SCsub
@@ -4,24 +4,9 @@ Import("env")
 
 env.scene_sources = []
 
-# Thirdparty code
-thirdparty_dir = "#thirdparty/misc/"
-thirdparty_sources = [
-    # C++ sources
-    "easing_equations.cpp",
-    # C sources
-    "mikktspace.c",
-]
-thirdparty_sources = [thirdparty_dir + file for file in thirdparty_sources]
-
-env_thirdparty = env.Clone()
-env_thirdparty.disable_warnings()
-env_thirdparty.add_source_files(env.scene_sources, thirdparty_sources)
-
-# Godot's own sources
+# Godot source files
 env.add_source_files(env.scene_sources, "*.cpp")
 
-
 # Chain load SCsubs
 SConscript("main/SCsub")
 SConscript("gui/SCsub")
@@ -32,7 +17,6 @@ SConscript("audio/SCsub")
 SConscript("resources/SCsub")
 SConscript("debugger/SCsub")
 
-
 # Build it all as a library
 lib = env.add_library("scene", env.scene_sources)
 env.Prepend(LIBS=[lib])
diff --git a/scene/animation/SCsub b/scene/animation/SCsub
index fc61250247..cc33a5af84 100644
--- a/scene/animation/SCsub
+++ b/scene/animation/SCsub
@@ -2,4 +2,23 @@
 
 Import("env")
 
-env.add_source_files(env.scene_sources, "*.cpp")
+# Thirdparty code
+
+thirdparty_obj = []
+
+thirdparty_sources = "#thirdparty/misc/easing_equations.cpp"
+
+env_thirdparty = env.Clone()
+env_thirdparty.disable_warnings()
+env_thirdparty.add_source_files(thirdparty_obj, thirdparty_sources)
+env.scene_sources += thirdparty_obj
+
+# Godot source files
+
+scene_obj = []
+
+env.add_source_files(scene_obj, "*.cpp")
+env.scene_sources += scene_obj
+
+# Needed to force rebuilding the scene files when the thirdparty code is updated.
+env.Depends(scene_obj, thirdparty_obj)
diff --git a/scene/resources/SCsub b/scene/resources/SCsub
index 3a86b22835..f4dc7a46fb 100644
--- a/scene/resources/SCsub
+++ b/scene/resources/SCsub
@@ -2,6 +2,25 @@
 
 Import("env")
 
-env.add_source_files(env.scene_sources, "*.cpp")
+# Thirdparty code
+
+thirdparty_obj = []
+
+thirdparty_sources = "#thirdparty/misc/mikktspace.c"
+
+env_thirdparty = env.Clone()
+env_thirdparty.disable_warnings()
+env_thirdparty.add_source_files(thirdparty_obj, thirdparty_sources)
+env.scene_sources += thirdparty_obj
+
+# Godot source files
+
+scene_obj = []
+
+env.add_source_files(scene_obj, "*.cpp")
+env.scene_sources += scene_obj
+
+# Needed to force rebuilding the scene files when the thirdparty code is updated.
+env.Depends(scene_obj, thirdparty_obj)
 
 SConscript("default_theme/SCsub")