adb: don't emulate fdevent or socketpair on Windows.

Change-Id: I16cf7d4427eb79f36db39e91f85402a268fa72f5
(cherry picked from commit 3777d2ecc05d397ca501f4ee296e4e66568bb1bd)
diff --git a/adb/adb_utils.cpp b/adb/adb_utils.cpp
index 8a16e51..26e376c 100644
--- a/adb/adb_utils.cpp
+++ b/adb/adb_utils.cpp
@@ -213,6 +213,7 @@
 }
 
 #if !defined(_WIN32)
+// Windows version provided in sysdeps_win32.cpp
 bool set_file_block_mode(int fd, bool block) {
     int flags = fcntl(fd, F_GETFL, 0);
     if (flags == -1) {