aux/util: Port logging for Android.

Now if u_logging is used, it goes to logcat.

CMakeLists.txt

···
 find_library(RT_LIBRARY rt)
 if(ANDROID)
 	find_library(ANDROID_LIBRARY android)
+	find_library(ANDROID_LOG_LIBRARY log)
 endif()
 
 # This one is named differently because that's what CTest uses

src/xrt/auxiliary/CMakeLists.txt

···
 else()
 	target_link_libraries(aux_util PUBLIC xrt-external-cjson)
 endif()
+if(ANDROID)
+	target_link_libraries(aux_util PUBLIC ${ANDROID_LOG_LIBRARY})
+endif()
 
 # Tracking library.
 add_library(aux_tracking STATIC ${TRACKING_SOURCE_FILES})

src/xrt/auxiliary/util/u_logging.c

···
  */
 
 #include "util/u_logging.h"
+#include "xrt/xrt_config_os.h"
 
 #include <assert.h>
 #include <stdio.h>
 #include <stdarg.h>
 
 
+#ifdef XRT_OS_ANDROID
+
+#include <android/log.h>
+
+static android_LogPriority
+u_log_convert_priority(enum u_logging_level level)
+{
+	switch (level) {
+	case U_LOGGING_TRACE: return ANDROID_LOG_VERBOSE;
+	case U_LOGGING_DEBUG: return ANDROID_LOG_DEBUG;
+	case U_LOGGING_INFO: return ANDROID_LOG_INFO;
+	case U_LOGGING_WARN: return ANDROID_LOG_WARN;
+	case U_LOGGING_ERROR: return ANDROID_LOG_ERROR;
+	case U_LOGGING_RAW: return ANDROID_LOG_INFO;
+	default: break;
+	}
+	return ANDROID_LOG_INFO;
+}
+void
+u_log(const char *file,
+      int line,
+      const char *func,
+      enum u_logging_level level,
+      const char *format,
+      ...)
+{
+	// print_prefix(func, level);
+	android_LogPriority prio = u_log_convert_priority(level);
+	va_list args;
+	va_start(args, format);
+	__android_log_vprint(prio, func, format, args);
+	va_end(args);
+}
+
+void
+u_log_xdev(const char *file,
+           int line,
+           const char *func,
+           enum u_logging_level level,
+           struct xrt_device *xdev,
+           const char *format,
+           ...)
+{
+	android_LogPriority prio = u_log_convert_priority(level);
+	va_list args;
+	va_start(args, format);
+	__android_log_vprint(prio, func, format, args);
+	va_end(args);
+}
+
+#else
 /*
  *
  * Helper functions.
···
 
 	fprintf(stderr, "\n");
 }
+#endif