[threading linux] Fix nanosleep using microseconds

Add Sleep Test for 50ms.
Fix Sleep under linux that was using microseconds as nanoseconds.
Factor timespec creation to template function using div/mod and nanoseconds
from duration cast.

src/xenia/base/testing/threading_test.cc

@@ -15,6 +15,7 @@ namespace xe {
 namespace base {
 namespace test {
 using namespace threading;
+using namespace std::chrono_literals;
 
 TEST_CASE("Fence") {
   // TODO(bwrsandman):
@@ -43,8 +44,11 @@ TEST_CASE("Sync with Memory Barrier", "SyncMemory") {
 }
 
 TEST_CASE("Sleep Current Thread", "Sleep") {
-  // TODO(bwrsandman):
+  auto wait_time = 50ms;
-  REQUIRE(true);
+  auto start = std::chrono::steady_clock::now();
+  Sleep(wait_time);
+  auto duration = std::chrono::steady_clock::now() - start;
+  REQUIRE(duration >= wait_time);
 }
 
 TEST_CASE("Sleep Current Thread in Alertable State", "Sleep") {

src/xenia/base/threading_posix.cc

@@ -23,6 +23,15 @@
 namespace xe {
 namespace threading {
 
+template <typename _Rep, typename _Period>
+inline timespec DurationToTimeSpec(
+    std::chrono::duration<_Rep, _Period> duration) {
+  auto nanoseconds =
+      std::chrono::duration_cast<std::chrono::nanoseconds>(duration);
+  auto div = ldiv(nanoseconds.count(), 1000000000L);
+  return timespec{div.quot, div.rem};
+}
+
 // TODO(dougvj)
 void EnableAffinityConfiguration() {}
 
@@ -47,8 +56,7 @@ void MaybeYield() {
 void SyncMemory() { __sync_synchronize(); }
 
 void Sleep(std::chrono::microseconds duration) {
-  timespec rqtp = {time_t(duration.count() / 1000000),
+  timespec rqtp = DurationToTimeSpec(duration);
-                   time_t(duration.count() % 1000)};
   nanosleep(&rqtp, nullptr);
   // TODO(benvanik): spin while rmtp >0?
 }