Fixed Mac build by running builders in subprocess only on Windows

Also passing serializable SCons environment variables (env) for compatibility with debug builds (search for uses of env in make functions)

platform_methods.py

@@ -7,9 +7,18 @@ import subprocess
 
 # NOTE: The multiprocessing module is not compatible with SCons due to conflict on cPickle
 
+if sys.version_info[0] < 3:
+    JSON_SERIALIZABLE_TYPES = (bool, int, long, float, basestring)
+else:
+    JSON_SERIALIZABLE_TYPES = (bool, int, float, str)
+
 
 def run_in_subprocess(builder_function):
 
+    # Run in subprocess only while running the build on Windows
+    if sys.platform not in ('win32', 'cygwin'):
+        return builder_function
+
     @functools.wraps(builder_function)
     def wrapper(target, source, env):
 
@@ -17,10 +26,6 @@ def run_in_subprocess(builder_function):
         target = [node.srcnode().abspath for node in target]
         source = [node.srcnode().abspath for node in source]
 
-        # Short circuit on non-Windows platforms
-        if os.name != 'nt':
-            return builder_function(target, source, None)
-
         # Identify module
         module_name = builder_function.__module__
         function_name = builder_function.__name__
@@ -32,14 +37,25 @@ def run_in_subprocess(builder_function):
         subprocess_env = os.environ.copy()
         subprocess_env['PYTHONPATH'] = os.pathsep.join([os.getcwd()] + sys.path)
 
+        # Keep only JSON serializable environment items
+        filtered_env = dict(
+            (key, value)
+            for key, value in env.items()
+            if isinstance(value, JSON_SERIALIZABLE_TYPES)
+        )
+
         # Save parameters
-        args = (target, source, None)
+        args = (target, source, filtered_env)
         data = dict(fn=function_name, args=args)
         json_path = os.path.join(os.environ['TMP'], uuid.uuid4().hex + '.json')
         with open(json_path, 'wt') as json_file:
             json.dump(data, json_file, indent=2)
+        json_file_size = os.stat(json_path).st_size
+
+        print('Executing builder function in subprocess: '
+              'module_path=%r, parameter_file=%r, parameter_file_size=%r, target=%r, source=%r' % (
+               module_path, json_path, json_file_size, target, source))
         try:
-            print('Executing builder function in subprocess: module_path=%r; data=%r' % (module_path, data))
             exit_code = subprocess.call([sys.executable, module_path, json_path], env=subprocess_env)
         finally:
             try: