appveyor: inspect binaries

appveyor.yml

@@ -17,6 +17,8 @@ test_script:
   - cargo build --release
   - cargo test
   - cargo test --release
+  - dumpbin /disasm target/debug/librustc_builtins.rlib
+  - dumpbin /disasm target/release/librustc_builtins.rlib
 
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