[util] Add platform-specific clock implementation

MinGW calls to GetSystemTimeAsFileTime via gettimeofday for std::chrono::high_resolution_clock::now,
This is horribly slow and inaccurate.

There are also issues if MinGW is not built with libstdc++ at the same time that can cause the precision to be bad enough to cause massive hangs.
This effectively works around that as well.

Relevant: ValveSoftware/Proton#3198

src/util/util_time.h

@@ -0,0 +1,50 @@
+#pragma once
+
+#include <chrono>
+#include <cstdint>
+
+#ifdef _WIN32
+#include <windows.h>
+#endif
+
+namespace dxvk {
+
+#ifdef _WIN32
+  struct high_resolution_clock {
+    static constexpr bool is_steady = true;
+
+    using rep        = int64_t;
+    using period     = std::nano;
+    using duration   = std::chrono::nanoseconds;
+    using time_point = std::chrono::time_point<high_resolution_clock>;
+
+    static inline time_point now() noexcept {
+      // Keep the frequency static, this doesn't change at all.
+      static const int64_t freq = getFrequency();
+      const int64_t counter     = getCounter();
+
+      const int64_t whole = (counter / freq) * period::den;
+      const int64_t part  = (counter % freq) * period::den / freq;
+
+      return time_point(duration(whole + part));
+    }
+
+    static inline int64_t getFrequency() {
+      LARGE_INTEGER freq;
+      QueryPerformanceFrequency(&freq);
+
+      return freq.QuadPart;
+    }
+
+    static inline int64_t getCounter() {
+      LARGE_INTEGER count;
+      QueryPerformanceCounter(&count);
+
+      return count.QuadPart;
+    }
+  };
+#else
+  using clock = std::chrono::high_resolution_clock;
+#endif
+
+}