hide nixide-sys tests behind feature flags

nixide-sys/tests/eval.rs

@@ -1,3 +1,4 @@
+#![cfg(feature = "nix-expr-c")]
 #![cfg(test)]
 
 use std::{

nixide-sys/tests/flake.rs

@@ -1,3 +1,4 @@
+#![cfg(feature = "nix-flake-c")]
 #![cfg(test)]
 
 use std::ptr;

nixide-sys/tests/memory.rs

@@ -1,3 +1,4 @@
+#![cfg(feature = "nix-expr-c")]
 #![cfg(test)]
 
 use std::ffi::CString;

nixide-sys/tests/primop.rs

@@ -1,3 +1,4 @@
+#![cfg(feature = "nix-expr-c")]
 #![cfg(test)]
 
 use std::{

nixide-sys/tests/store.rs

@@ -1,3 +1,4 @@
+#![cfg(feature = "nix-store-c")]
 #![cfg(test)]
 
 use std::{ffi::CString, ptr};