add comment about hardcoded default target in fake-releases

Author: syphar

src/test/fakes.rs

@@ -325,6 +325,10 @@ impl<'a> FakeRelease<'a> {
         if let Some(markdown) = self.readme {
             fs::write(crate_dir.join("README.md"), markdown)?;
         }
+
+        // Many tests rely on the default-target being linux, so it should not
+        // be set to docsrs_metadata::HOST_TARGET, because then tests fail on all
+        // non-linux platforms.
         let default_target = self.default_target.unwrap_or("x86_64-unknown-linux-gnu");
         let release_id = crate::db::add_package_into_database(
             &mut db.conn(),