Pass the arch rather than full target name to windows_registry::find_tool

The full target name can be anything with custom target specs. Passing
just the arch wasn't possible before cc 1.2, but is now.

Author: bjorn3

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -1021,12 +1021,8 @@ fn link_natively(
                         && (code < 1000 || code > 9999)
                     {
                         let is_vs_installed = windows_registry::find_vs_version().is_ok();
-                        // FIXME(cc-rs#1265) pass only target arch to find_tool()
-                        let has_linker = windows_registry::find_tool(
-                            sess.opts.target_triple.tuple(),
-                            "link.exe",
-                        )
-                        .is_some();
+                        let has_linker =
+                            windows_registry::find_tool(&sess.target.arch, "link.exe").is_some();
 
                         sess.dcx().emit_note(errors::LinkExeUnexpectedError);
                         if is_vs_installed && has_linker {

compiler/rustc_codegen_ssa/src/back/linker.rs

@@ -50,8 +50,7 @@ pub(crate) fn get_linker<'a>(
     self_contained: bool,
     target_cpu: &'a str,
 ) -> Box<dyn Linker + 'a> {
-    // FIXME(cc-rs#1265) pass only target arch to find_tool()
-    let msvc_tool = windows_registry::find_tool(sess.opts.target_triple.tuple(), "link.exe");
+    let msvc_tool = windows_registry::find_tool(&sess.target.arch, "link.exe");
 
     // If our linker looks like a batch script on Windows then to execute this
     // we'll need to spawn `cmd` explicitly. This is primarily done to handle