Merge pull request 'Implement variadic functions for Win64 in the x86_64 backend' (#31672) from kcbanner/zig:win64_varargs into master

Reviewed-on: https://codeberg.org/ziglang/zig/pulls/31672
Reviewed-by: Andrew Kelley <andrew@ziglang.org>

lib/std/zig.zig

@@ -986,11 +986,14 @@ pub const EmitArtifact = enum {
     docs,
     pdb,
     h,
+    compiler_rt_dyn_lib,
 
     /// If using `Server` to communicate with the compiler, it will place requested artifacts in
     /// paths under the output directory, where those paths are named according to this function.
     /// Returned string is allocated with `gpa` and owned by the caller.
     pub fn cacheName(ea: EmitArtifact, gpa: Allocator, opts: BinNameOptions) Allocator.Error![]const u8 {
+        // hack for stage2_x86_64 + coff. See Coff.flush.
+        if (ea == .compiler_rt_dyn_lib) return "compiler_rt.dll";
         const suffix: []const u8 = switch (ea) {
             .bin => return binNameAlloc(gpa, opts),
             .@"asm" => ".s",
@@ -1000,6 +1003,7 @@ pub const EmitArtifact = enum {
             .docs => "-docs",
             .pdb => ".pdb",
             .h => ".h",
+            .compiler_rt_dyn_lib => unreachable,
         };
         return std.fmt.allocPrint(gpa, "{s}{s}", .{ opts.root_name, suffix });
     }