fix msvc

examples/cfunc.rs

@@ -0,0 +1,15 @@
+extern crate mruby_compiler2_sys;
+use mruby_compiler2_sys::MRubyCompiler2Context;
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    unsafe {
+        let mut cxt = MRubyCompiler2Context::new();
+        cxt.compile_to_c_function(
+            "puts \"Hello, mruby-compiler2!\"",
+            "init_test_func",
+            std::path::Path::new("examples/out.c"),
+        )?;
+    }
+    println!("Created examples/out.c");
+    Ok(())
+}