appveyor: Don't test i586 MSVC binaries yet

I was hoping

Author: alexcrichton

appveyor.yml

@@ -12,7 +12,7 @@ environment:
     DEPLOY: 1
   - MSYS_BITS: 32
     RUST_CONFIGURE_ARGS: --build=i686-pc-windows-msvc --target=i586-pc-windows-msvc
-    SCRIPT: python x.py test && python x.py dist
+    SCRIPT: python x.py test --host i686-pc-windows-msvc --target i686-pc-windows-msvc && python x.py dist
     DEPLOY: 1
 
   # MSVC makefiles