vendor : apply patches for subprocess.h (#26606)

vendor/sheredom/patch-bsd.patch

@@ -0,0 +1,19 @@
+Fix build on NetBSD, which provides posix_spawn_file_actions_addchdir()
+but not the _np() variant.
+
+Upstream PR: https://github.com/sheredom/subprocess.h/pull/102
+Applied locally by scripts/sync_vendor.py until it is merged upstream.
+
+diff --git a/subprocess.h b/subprocess.h
+index 5e809023a4..74a4e006c7 100644
+--- a/subprocess.h
++++ b/subprocess.h
+@@ -1205,7 +1205,7 @@ cleanup:
+ 
+   // Set working directory
+   if (process_cwd) {
+-#if defined(__APPLE__) && MAC_OS_X_VERSION_MIN_REQUIRED >= 260000
++#if defined(__NetBSD__) || (defined(__APPLE__) && MAC_OS_X_VERSION_MIN_REQUIRED >= 260000)
+     posix_error = posix_spawn_file_actions_addchdir(&actions, process_cwd);
+ #else
+ #if defined(__APPLE__) && defined(__clang__)