Fixed the Windows build of protoc by statically linking deps.

BUILD.bazel

@@ -6,7 +6,7 @@ load("@rules_pkg//:mappings.bzl", "pkg_files", "strip_prefix")
 load("@rules_proto//proto:defs.bzl", "proto_lang_toolchain", "proto_library")
 load("@rules_python//python:defs.bzl", "py_library")
 load("@rules_java//java:defs.bzl", "java_binary", "java_lite_proto_library", "java_proto_library")
-load("//build_defs:cpp_opts.bzl", "COPTS", "LINK_OPTS")
+load("//build_defs:cpp_opts.bzl", "COPTS", "LINK_OPTS", "PROTOC_LINK_OPTS")
 load(
     ":protobuf.bzl",
     "adapt_proto_library",
@@ -442,7 +442,7 @@ cc_library(
 cc_binary(
     name = "protoc",
     srcs = ["src/google/protobuf/compiler/main.cc"],
-    linkopts = LINK_OPTS,
+    linkopts = LINK_OPTS + PROTOC_LINK_OPTS,
     visibility = ["//visibility:public"],
     deps = [":protoc_lib"],
 )

build_defs/BUILD.bazel

@@ -59,6 +59,20 @@ config_setting(
     },
 )
 
+config_setting(
+    name = "config_win32",
+    values = {
+        "cpu": "win32",
+    },
+)
+
+config_setting(
+    name = "config_win64",
+    values = {
+        "cpu": "win64",
+    },
+)
+
 # Internal testing:
 
 starlark_cc_proto_library(

build_defs/cpp_opts.bzl

@@ -38,3 +38,10 @@ LINK_OPTS = select({
         "-lm",
     ],
 })
+
+# When cross-compiling for Windows we need to statically link pthread and the C++ library.
+PROTOC_LINK_OPTS = select({
+    "//build_defs:config_win32": ["-static"],
+    "//build_defs:config_win64": ["-static"],
+    "//conditions:default": [],
+})