Starlarkify Proto flags.

BEGIN_PUBLIC
  Internal Change
END_PUBLIC

PiperOrigin-RevId: 823942826
Change-Id: Ib8a060fc0faa377582a2600c91ed788c4baa91f6

Author: susinmotion

src/test/java/com/google/devtools/build/lib/packages/util/MockProtoSupport.java

@@ -41,6 +41,9 @@ public static void setup(MockToolsConfig config) throws IOException {
     createNetProto2(config);
     setupWorkspace(config);
     registerProtoToolchain(config);
+    // copybara:strip_begin(internal-only)
+    createProtoFlags(config);
+    // copybara:strip_end
   }
 
   private static void registerProtoToolchain(MockToolsConfig config) throws IOException {
@@ -55,6 +58,79 @@ private static void registerProtoToolchain(MockToolsConfig config) throws IOExce
             + "')");
   }
 
+  // copybara:strip_begin(internal-only)
+  private static void createProtoFlags(MockToolsConfig config) throws IOException {
+    config.create(
+        "third_party/protobuf/bazel/flags/java/mutable/BUILD",
+        """
+        label_flag(
+            name = "proto_toolchain_for_javamutable",
+            build_setting_default = "//tools/proto/toolchains:javamutable",
+        )
+
+        label_flag(
+            name = "proto_toolchain_for_javamutable_with_stubby1",
+            build_setting_default = "//tools/proto/toolchains:javamutable_with_stubby1",
+        )
+
+        label_flag(
+            name = "proto_toolchain_for_javamutable_with_stubby3",
+            build_setting_default = "//tools/proto/toolchains:javamutable_with_stubby3",
+        )
+
+        label_flag(
+            name = "proto_toolchain_for_javamutable_with_stubby13",
+            build_setting_default = "//tools/proto/toolchains:javamutable_with_stubby13",
+        )
+        """);
+    config.create(
+        "third_party/protobuf/bazel/flags/BUILD",
+        """
+        load("//third_party/bazel_skylib/rules:common_settings.bzl", "bool_flag")
+
+        cc_binary(
+            name = "empty",
+            srcs = ["empty_cc_plugin.cc"],
+        )
+
+        bool_flag(
+            name = "emit_proto_annotation_metadata",
+            build_setting_default = False,
+        )
+        """);
+    config.create(
+        "third_party/protobuf/bazel/flags/cc/BUILD",
+        """
+        load("//third_party/bazel_skylib/rules:common_settings.bzl", "bool_flag")
+
+        bool_flag(
+            name = "dual_proto_modules",
+            build_setting_default = False,
+        )
+
+        label_flag(
+            name = "protoc_cc_lib",
+            build_setting_default = ":empty",
+        )
+
+        label_flag(
+            name = "protoc_cc_plugin",
+            build_setting_default = ":empty",
+        )
+
+        bool_flag(
+            name = "experimental_proto_static_reflection_h",
+            build_setting_default = False,
+        )
+
+        sh_binary(
+            name = "empty",
+            srcs = ["empty.sh"],
+        )
+        """);
+  }
+
+  // copybara:strip_end
   /**
    * Create a dummy net/proto2 compiler, a dummy protoc_minimal and proto APIs for all languages and
    * versions.