test --no-default-features and fix musl builds

appveyor.yml

@@ -24,4 +24,5 @@ build: false
 
 test_script:
   - cargo test --target %TARGET%
+  - cargo test --no-default-features --target %TARGET%
   - cargo test --manifest-path libc-test/Cargo.toml --target %TARGET%

ci/run.sh

@@ -79,4 +79,5 @@ if [ "$TARGET" = "x86_64-unknown-linux-gnux32" ]; then
   opt="--release"
 fi
 
+exec cargo test $opt --no-default-features --target $TARGET
 exec cargo test $opt --manifest-path libc-test/Cargo.toml --target $TARGET

src/unix/mod.rs

@@ -277,8 +277,8 @@ cfg_if! {
         // cargo build, don't pull in anything extra as the libstd dep
         // already pulls in all libs.
     } else if #[cfg(target_env = "musl")] {
-        #[link(name = "c", kind = "static", cfg(target_feature = "crt-static"))]
-        #[link(name = "c", cfg(not(target_feature = "crt-static")))]
+        #[cfg_attr(feature = "stdbuild", link(name = "c", kind = "static", cfg(target_feature = "crt-static")))]
+        #[cfg_attr(feature = "stdbuild", link(name = "c", cfg(not(target_feature = "crt-static"))))]
         extern {}
     } else if #[cfg(target_os = "emscripten")] {
         #[link(name = "c")]