Add LLVM based mingw-w64 targets

library/unwind/src/lib.rs

@@ -5,6 +5,7 @@
 #![feature(nll)]
 #![feature(staged_api)]
 #![feature(c_unwind)]
+#![feature(cfg_target_abi)]
 #![cfg_attr(not(target_env = "msvc"), feature(libc))]
 
 cfg_if::cfg_if! {
@@ -85,3 +86,7 @@ extern "C" {}
 #[cfg(all(target_vendor = "fortanix", target_env = "sgx"))]
 #[link(name = "unwind", kind = "static", modifiers = "-bundle")]
 extern "C" {}
+
+#[cfg(all(target_os = "windows", target_env = "gnu", target_abi = "llvm"))]
+#[link(name = "unwind", kind = "static", modifiers = "-bundle")]
+extern "C" {}