Replace CLOCK_MONOTONIC with SYSTEM_TIME_MONOTONIC

Using SYSTEM_TIME_MONOTONIC works for Android (where it translates to
CLOCK_MONOTONIC) and host targets, while CLOCK_MONOTONIC is not defined
on macOS.

Bug: 117921091
Test: existing tests should pass
Change-Id: I1fad472881830fb0701a320cf37319e083932ad4
diff --git a/libs/hwui/renderthread/RenderThread.cpp b/libs/hwui/renderthread/RenderThread.cpp
index 8638142..ee1a7ce 100644
--- a/libs/hwui/renderthread/RenderThread.cpp
+++ b/libs/hwui/renderthread/RenderThread.cpp
@@ -103,7 +103,7 @@
                                            [this]() { mRenderThread->drainDisplayEventQueue(); });
     }
 
-    virtual nsecs_t latestVsyncEvent() override { return systemTime(CLOCK_MONOTONIC); }
+    virtual nsecs_t latestVsyncEvent() override { return systemTime(SYSTEM_TIME_MONOTONIC); }
 
 private:
     RenderThread* mRenderThread;