test --no-default-features and fix musl builds
diff --git a/appveyor.yml b/appveyor.yml
index 07ac4a9..fe2a332 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -24,4 +24,5 @@
 
 test_script:
   - cargo test --target %TARGET%
+  - cargo test --no-default-features --target %TARGET%
   - cargo test --manifest-path libc-test/Cargo.toml --target %TARGET%