[adb] generic "cast_handle_to_int" function

Now one can use it without platform #ifdefs

Bug: 150183149
Test: compiles
Change-Id: I6280dcdd2faaff33014f11237d9d04231ac16b82
diff --git a/adb/transport.cpp b/adb/transport.cpp
index ed4a93b..6dccb7f 100644
--- a/adb/transport.cpp
+++ b/adb/transport.cpp
@@ -500,12 +500,8 @@
     auto x509 = GenerateX509Certificate(evp_pkey.get());
     auto x509_str = X509ToPEMString(x509.get());
     auto evp_str = Key::ToPEMString(evp_pkey.get());
-#ifdef _WIN32
-    int osh = cast_handle_to_int(adb_get_os_handle(fd_));
-#else
-    int osh = adb_get_os_handle(fd_);
-#endif
 
+    int osh = cast_handle_to_int(adb_get_os_handle(fd_));
 #if ADB_HOST
     tls_ = TlsConnection::Create(TlsConnection::Role::Client,
 #else