Adds #include <umachine.h> to LocaleListCache.cpp

This adds the header which defines the constants TRUE and FALSE.  Recent
changes to the ICU library (ICU 68.1) have apparently made the constants
inaccessible transitively via uloc.h, leading to a compilation break.

I discovered this accidentally while upgrading Flutter engine to ICU
68.1: https://github.com/flutter/engine/pull/22466

Change-Id: Ib92c13bd836d77a6fa34d99209eabbbab380abcc
diff --git a/libs/minikin/LocaleListCache.cpp b/libs/minikin/LocaleListCache.cpp
index 15156cd..e4adb12 100644
--- a/libs/minikin/LocaleListCache.cpp
+++ b/libs/minikin/LocaleListCache.cpp
@@ -22,6 +22,7 @@
 
 #include <log/log.h>
 #include <unicode/uloc.h>
+#include <unicode/umachine.h>
 
 #include "Locale.h"
 #include "MinikinInternal.h"