rust/ostree-sys: regenerate for gtk-rs 0.15

rust-bindings/sys/tests/abi.rs

@@ -110,6 +110,7 @@ impl Results {
 }
 
 #[test]
+#[cfg(target_os = "linux")]
 fn cross_validate_constants_with_c() {
     let mut c_constants: Vec<(String, String)> = Vec::new();
 
@@ -150,6 +151,7 @@ fn cross_validate_constants_with_c() {
 }
 
 #[test]
+#[cfg(target_os = "linux")]
 fn cross_validate_layout_with_c() {
     let mut c_layouts = Vec::new();