Add Betsy to speed up BC6 compression

modules/betsy/SCsub

@@ -0,0 +1,24 @@
+# !/ usr / bin / env python
+Import("env")
+Import("env_modules")
+
+env_betsy = env_modules.Clone()
+env_betsy.GLSL_HEADER("bc6h.glsl")
+env_betsy.Depends(Glob("*.glsl.gen.h"), ["#glsl_builders.py"])
+
+# Thirdparty source files
+thirdparty_obj = []
+thirdparty_dir = "#thirdparty/betsy/"
+env_betsy.Prepend(CPPPATH=[thirdparty_dir])
+
+env_thirdparty = env_betsy.Clone()
+env_thirdparty.disable_warnings()
+env.modules_sources += thirdparty_obj
+
+# Godot source files
+module_obj = []
+env_betsy.add_source_files(module_obj, "*.cpp")
+env.modules_sources += module_obj
+
+# Needed to force rebuilding the module files when the thirdparty library is updated.
+env.Depends(module_obj, thirdparty_obj)