Fixed printf build warning.

llvm-svn: 183250
diff --git a/lldb/source/Expression/IRMemoryMap.cpp b/lldb/source/Expression/IRMemoryMap.cpp
index a8c9493..e3f6178 100644
--- a/lldb/source/Expression/IRMemoryMap.cpp
+++ b/lldb/source/Expression/IRMemoryMap.cpp
@@ -677,7 +677,7 @@
         {
         default:
             error.SetErrorToGenericError();
-            error.SetErrorStringWithFormat("Couldn't read scalar: unsupported size %" PRId64, size);
+            error.SetErrorStringWithFormat("Couldn't read scalar: unsupported size %" PRIu64, (uint64_t)size);
             return;
         case 1: scalar = extractor.GetU8(&offset);  break;
         case 2: scalar = extractor.GetU16(&offset); break;