Fix a couple of incorrect format string warnings

This patch fixes use of incorrect `%zi` to format a plain `int`, and using
`%llu` to format a `uint64_t`. The fix is to use the new typesafe
`llvm::Formatv` based API.

Differential Revision: https://reviews.llvm.org/D28028
Subscribers: lldb-commits

llvm-svn: 290359
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/IRForTarget.cpp b/lldb/source/Plugins/ExpressionParser/Clang/IRForTarget.cpp
index 4f41c8e..356e2e7 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/IRForTarget.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/IRForTarget.cpp
@@ -513,8 +513,8 @@
  default:
    encoding_flags = 0x0600; /* fall back to 0x0600, kCFStringEncodingASCII */
    if (log) {
-     log->Printf("Encountered an Objective-C constant string with unusual "
-                 "element size %llu",
+     log->Format("Encountered an Objective-C constant string with unusual "
+                 "element size {0}",
                  string_array->getElementByteSize());
    }
  }