--- a/engine/SCons/Platform/__init__.py
+++ b/engine/SCons/Platform/__init__.py
@@ -65,6 +65,8 @@ def platform_default():
     care about the machine architecture.
     """
     osname = os.name
+    if 'PLATFORM' in os.environ:
+        return os.environ['PLATFORM']
     if osname == 'java':
         osname = os._osType
     if osname == 'posix':