Adjust thread name column width depending on real name length.

Make 16-byte aligned field instead of truncating a name to 16 byte.

llvm-svn: 336993
diff --git a/lldb/source/Utility/Log.cpp b/lldb/source/Utility/Log.cpp
index abc022a..eb026fb 100644
--- a/lldb/source/Utility/Log.cpp
+++ b/lldb/source/Utility/Log.cpp
@@ -286,7 +286,11 @@
   if (options.Test(LLDB_LOG_OPTION_PREPEND_THREAD_NAME)) {
     llvm::SmallString<32> thread_name;
     llvm::get_thread_name(thread_name);
-    OS << llvm::formatv("{0,-16} ", thread_name);
+
+    llvm::SmallString<12> format_str;
+    llvm::raw_svector_ostream format_os(format_str);
+    format_os << "{0,-" << llvm::alignTo<16>(thread_name.size()) << "} ";
+    OS << llvm::formatv(format_str.c_str(), thread_name);
   }
 
   if (options.Test(LLDB_LOG_OPTION_BACKTRACE))