EmulatedFiles: Emulate current_clocksource

WINE uses this to determine TSC frequency and because it doesn't say
`tsc` on ARM devices, it was ignoring TSC and instead using CPU maximum
frequency.

This was causing Horizon to think the TSC ran at whatever the max
frequency of a core was  (1.8Ghz to 2.6Ghz depending?) This was causing
all of Horizon Zero Dawn's physics to run at slower than real time
speeds because our 1Ghz (on Orion) TSC is significantly lower than the
max clock speeds of the cores.

This is still a bug in Wine that it is using the maximum CPU clock speed
in the case of current_clocksource not being TSC, but that's a battle
for a different time.

Source/Tools/LinuxEmulation/LinuxSyscalls/EmulatedFiles/EmulatedFiles.cpp

@@ -545,6 +545,19 @@ EmulatedFDManager::EmulatedFDManager(FEXCore::Context::Context* ctx)
     return FD;
   };
 
+  // Wine reads this to ensure TSC is trusted by the kernel. Otherwise it falls back to maximum clock speed of the CPU cores.
+  // Without this, games like Horizon Zero Dawn would run their physics in slow-motion.
+  FDReadCreators["/sys/devices/system/clocksource/clocksource0/current_clocksource"] =
+    [&](FEXCore::Context::Context* ctx, int32_t fd, const char* pathname, int32_t flags, mode_t mode) -> int32_t {
+    int FD = GenTmpFD(pathname, flags);
+    const char source[] = "tsc\n";
+    // + 1 to ensure null at the end
+    write(FD, source, strlen(source) + 1);
+    lseek(FD, 0, SEEK_SET);
+    SealTmpFD(FD);
+    return FD;
+  };
+
   auto NumCPUCores = [&](FEXCore::Context::Context* ctx, int32_t fd, const char* pathname, int32_t flags, mode_t mode) -> int32_t {
     int FD = GenTmpFD(pathname, flags);
     write(FD, (void*)&cpus_online.at(0), cpus_online.size());