[9.0.2] Include both windows and unix files in embedded_zipper_sources (#29235)

### Description

This filegroup is being built for user's exec platform, which can be
different from bazel's platform (= user's host platform). The `select()`
selects with bazel's platform, making it impossible to build bazel's
internal tools for a different platform.

### Motivation

This fixes the "input file not found" error when building with a remote
execution platform that is different from the host.

### Build API Changes

No

### Checklist

- [ ] I have added tests for the new use cases (if any).
- [ ] I have updated the documentation (if applicable).

### Release Notes

RELNOTES: None

Closes #29057.

PiperOrigin-RevId: 890318692
Change-Id: Ibfd0ae8d934e2e0ca9726a0ee907b4791c346504

---------

Co-authored-by: Zach Yu <zachyu@google.com>

Author: iancha1992

src/main/cpp/util/port.h

@@ -141,7 +141,10 @@ char (&ArraySizeHelper(const T (&array)[N]))[N];
 // either by making PID handling platform-independent or some other idea; remove
 // the following typedef afterwards.
 #ifndef __MINGW32__
+#ifndef _PID_T_
+#define _PID_T_
 typedef int pid_t;
+#endif  // _PID_T_
 #endif  // __MINGW32__
 #endif  // _WIN32
 

third_party/ijar/BUILD

@@ -101,21 +101,16 @@ filegroup(
         "BUILD",
         "common.h",
         "mapped_file.h",
+        "mapped_file_unix.cc",
+        "mapped_file_windows.cc",
         "platform_utils.cc",
         "platform_utils.h",
         "zip.cc",
         "zip.h",
         "zip_main.cc",
         "zlib_client.cc",
         "zlib_client.h",
-    ] + select({
-        "//src/conditions:windows": [
-            "mapped_file_windows.cc",
-        ],
-        "//conditions:default": [
-            "mapped_file_unix.cc",
-        ],
-    }),
+    ],
     visibility = ["//visibility:public"],
 )