Coff linker: Add IMPLIB support

Allow --out-implib as passed by cmake and meson to be correctly passed
through to the linker to generate import libraries.

src/Compilation.zig

@@ -724,6 +724,7 @@ pub const InitOptions = struct {
     test_filter: ?[]const u8 = null,
     test_name_prefix: ?[]const u8 = null,
     subsystem: ?std.Target.SubSystem = null,
+    out_implib: ?[]const u8 = null,
     /// WASI-only. Type of WASI execution model ("command" or "reactor").
     wasi_exec_model: ?std.builtin.WasiExecModel = null,
 };
@@ -1364,6 +1365,7 @@ pub fn create(gpa: *Allocator, options: InitOptions) !*Compilation {
             .each_lib_rpath = options.each_lib_rpath orelse options.is_native_os,
             .disable_lld_caching = options.disable_lld_caching,
             .subsystem = options.subsystem,
+            .out_implib = options.out_implib,
             .is_test = options.is_test,
             .wasi_exec_model = wasi_exec_model,
             .use_stage1 = use_stage1,

src/link.zig

@@ -98,6 +98,7 @@ pub const Options = struct {
     gc_sections: ?bool = null,
     allow_shlib_undefined: ?bool,
     subsystem: ?std.Target.SubSystem,
+    out_implib: ?[]const u8,
     linker_script: ?[]const u8,
     version_script: ?[]const u8,
     soname: ?[]const u8,

src/link/Coff.zig

@@ -888,6 +888,7 @@ fn linkWithLLD(self: *Coff, comp: *Compilation) !void {
         man.hash.add(self.base.options.dynamicbase);
         man.hash.addOptional(self.base.options.major_subsystem_version);
         man.hash.addOptional(self.base.options.minor_subsystem_version);
+        man.hash.addOptionalBytes(self.base.options.out_implib);
 
         // We don't actually care whether it's a cache hit or miss; we just need the digest and the lock.
         _ = try man.hit();
@@ -1020,8 +1021,8 @@ fn linkWithLLD(self: *Coff, comp: *Compilation) !void {
             }
         }
 
-        for (self.base.options.lib_dirs) |lib_dir| {
-            try argv.append(try allocPrint(arena, "-LIBPATH:{s}", .{lib_dir}));
+        if (self.base.options.out_implib) |out_implib| {
+            try argv.append(try allocPrint(arena, "-IMPLIB:{s}", .{out_implib}));
         }
 
         try argv.appendSlice(self.base.options.objects);
@@ -1034,6 +1035,10 @@ fn linkWithLLD(self: *Coff, comp: *Compilation) !void {
             try argv.append(p);
         }
 
+        for (self.base.options.lib_dirs) |lib_dir| {
+            try argv.append(try allocPrint(arena, "-LIBPATH:{s}", .{lib_dir}));
+        }
+
         const resolved_subsystem: ?std.Target.SubSystem = blk: {
             if (self.base.options.subsystem) |explicit| break :blk explicit;
             switch (target.os.tag) {

src/main.zig

@@ -611,6 +611,7 @@ fn buildOutputType(
     var main_pkg_path: ?[]const u8 = null;
     var clang_preprocessor_mode: Compilation.ClangPreprocessorMode = .no;
     var subsystem: ?std.Target.SubSystem = null;
+    var out_implib: ?[]const u8 = null;
     var major_subsystem_version: ?u32 = null;
     var minor_subsystem_version: ?u32 = null;
     var wasi_exec_model: ?std.builtin.WasiExecModel = null;
@@ -1476,6 +1477,12 @@ fn buildOutputType(
                     ) catch |err| {
                         fatal("unable to parse '{s}': {s}", .{ arg, @errorName(err) });
                     };
+                } else if (mem.eql(u8, arg, "--out-implib")) {
+                    i += 1;
+                    if (i >= linker_args.items.len) {
+                        fatal("expected linker arg after '{s}'", .{arg});
+                    }
+                    out_implib = linker_args.items[i];
                 } else {
                     warn("unsupported linker arg: {s}", .{arg});
                 }
@@ -2069,6 +2076,7 @@ fn buildOutputType(
         .test_name_prefix = test_name_prefix,
         .disable_lld_caching = !have_enable_cache,
         .subsystem = subsystem,
+        .out_implib = out_implib,
         .wasi_exec_model = wasi_exec_model,
     }) catch |err| {
         fatal("unable to create compilation: {s}", .{@errorName(err)});