Add gcc link when using crt-static

src/libunwind/lib.rs

@@ -31,6 +31,7 @@
 extern {}
 
 #[cfg(target_os = "redox")]
+#[link(name = "gcc", kind = "static-nobundle", cfg(target_feature = "crt-static"))]
 #[link(name = "gcc_eh", kind = "static-nobundle", cfg(target_feature = "crt-static"))]
 #[link(name = "gcc_s", cfg(not(target_feature = "crt-static")))]
 extern {}