[Support][Chrono] Use explicit cast of text output of time values.

[sdardis]

Summary

rL316419 exposed a platform specific issue where the type of the values
passed to llvm::format could be different to the format string.

Debian unstable for mips uses long long int for std::chrono:duration,
while x86_64 uses long int.

For mips, this resulted in the value being corrupted when rendered to a
string. Address this by explicitly casting the result of the duration_cast
to the type specified in the format string.

[sammccall]

Oh, good catch! Thanks for looking into this, and sorry for the bad diagnosis.

lib/Support/Chrono.cpp

void format_provider<TimePoint<>>::format(const TimePoint<> &T, raw_ostream &OS,
   // Handle extensions first. strftime mangles unknown %x on some platforms.
   if (Style.empty()) Style = "%Y-%m-%d %H:%M:%S.%N";
   std::string Format;
   raw_string_ostream FStream(Format);
   for (unsigned I = 0; I < Style.size(); ++I) {
     if (Style[I] == '%' && Style.size() > I + 1) switch (Style[I + 1]) {
         case 'L':  // Milliseconds, from Ruby.
           FStream << llvm::format(
-              "%.3lu", duration_cast<milliseconds>(Fractional).count());
+              "%.3lu", (long)duration_cast<milliseconds>(Fractional).count());
           ++I;
           continue;
         case 'f':  // Microseconds, from Python.
           FStream << llvm::format(
-              "%.6lu", duration_cast<microseconds>(Fractional).count());
+              "%.6lu", (long)duration_cast<microseconds>(Fractional).count());
           ++I;
           continue;
         case 'N':  // Nanoseconds, from date(1).
           FStream << llvm::format(
-              "%.6lu", duration_cast<nanoseconds>(Fractional).count());
+              "%.6lu", (long)duration_cast<nanoseconds>(Fractional).count());
           ++I;
           continue;
         case '%':  // Consume %%, so %%f parses as (%%)f not %(%f)
           FStream << "%%";
           ++I;
           continue;
       }
     FStream << Style[I];
   }
   FStream.flush();
   char Buffer[256];  // Should be enough for anywhen.
   size_t Len = strftime(Buffer, sizeof(Buffer), Format.c_str(), &LT);
   OS << (Len ? Buffer : "BAD-DATE-FORMAT");
 }
 
 } // namespace llvm