Use -windows-gnu for all UEFI targets

This restores the behavior prior to
rust-lang#1252, when the UEFI targets were
hardcoded in src/lib.rs.

dev-tools/gen-target-info/src/main.rs

@@ -26,17 +26,19 @@ fn generate_target_mapping(f: &mut File, target_specs: &RustcTargetSpecs) -> std
         let env = spec.env.as_deref().unwrap_or("");
         let abi = spec.abi.as_deref().unwrap_or("");
 
-        // Remove deployment target information from LLVM target triples (we
-        // will add this in another part of CC).
-        //
-        // FIXME(madsmtm): Should become unnecessary after
-        // https://github.com/rust-lang/rust/pull/131037
         let unversioned_llvm_target = if spec.llvm_target.contains("apple") {
+            // Remove deployment target information from LLVM target triples (we
+            // will add this in another part of CC).
+            //
+            // FIXME(madsmtm): Should become unnecessary after
+            // https://github.com/rust-lang/rust/pull/131037
             let mut components = spec.llvm_target.split("-").collect::<Vec<_>>();
 
             components[2] = components[2].trim_end_matches(|c: char| c.is_numeric() || c == '.');
 
             components.join("-")
+        } else if os == "uefi" && spec.llvm_target.ends_with("windows") {
+            format!("{}-gnu", spec.llvm_target)
         } else {
             spec.llvm_target.clone()
         };

src/target/generated.rs

@@ -409,7 +409,7 @@ pub(crate) const LIST: &[(&str, TargetInfo<'static>)] = &[
             os: "uefi",
             env: "",
             abi: "",
-            unversioned_llvm_target: "aarch64-unknown-windows",
+            unversioned_llvm_target: "aarch64-unknown-windows-gnu",
         },
     ),
     (
@@ -3205,7 +3205,7 @@ pub(crate) const LIST: &[(&str, TargetInfo<'static>)] = &[
             os: "uefi",
             env: "",
             abi: "",
-            unversioned_llvm_target: "x86_64-unknown-windows",
+            unversioned_llvm_target: "x86_64-unknown-windows-gnu",
         },
     ),
     (