scons: Avoid depending on scons 2.0 in general.
diff --git a/SConstruct b/SConstruct
index 96dc09a..8607d2c 100644
--- a/SConstruct
+++ b/SConstruct
@@ -153,7 +153,9 @@
     if host_env['msvc']:
         host_env.Append(CPPPATH = ['#include/c99'])
 
-    Export(env = host_env)
+    target_env = env
+    env = host_env
+    Export('env')
 
     SConscript(
         'src/SConscript',
@@ -161,6 +163,8 @@
         duplicate = 0, # http://www.scons.org/doc/0.97/HTML/scons-user/x2261.html
     )
 
+    env = target_env
+
 Export('env')
 
 #######################################################################