static_cast value to microsecond type (#73595)

Summary:
Pull Request resolved: pytorch/pytorch#73595

In some platforms, this might be a distinct type from 64-bit signed
integral, and the compiler might warn about implicit coercion.

Test Plan: Imported from OSS

Reviewed By: malfet

Differential Revision: D34558344

Pulled By: dagitses

fbshipit-source-id: 7a07d0723688390a7f27e6e71480d22c1e077200
(cherry picked from commit 8b807c4431f909c20b3133a6522b58d7b9ab0d85)

torch/csrc/distributed/c10d/TCPStore.cpp

@@ -893,7 +893,9 @@ void TCPClient::setTimeout(std::chrono::milliseconds value) {
       static_cast<long>((value.count() % 1000) * 1000)};
 #else
   struct timeval timeoutTV = {
-      .tv_sec = value.count() / 1000, .tv_usec = (value.count() % 1000) * 1000};
+      .tv_sec = value.count() / 1000,
+      .tv_usec = static_cast<suseconds_t>((value.count() % 1000) * 1000),
+  };
 #endif
   SYSCHECK_ERR_RETURN_NEG1(::setsockopt(
       socket_.handle(),