Windows: posix_trace_marker.c left to Linux, as the other posix_*.c

The Windows build takes the Linux platform layer's sources but those it replaces; the trace_marker refusal is glibc's open(), which Windows does not have.

port/windows/port.json

@@ -7,7 +7,8 @@
     "msvc_crt.c",
     "msvc_wide.c",
     "posix_update.c",
-    "posix_upnp.c"
+    "posix_upnp.c",
+    "posix_trace_marker.c"
   ],
   "libraries": [
     "ws2_32",