diagtool/CMakeLists.txt: Add missing tblgen'd dependency, ClangDiagnosticIndexName.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@158649 91177308-0d34-0410-b5e6-96231b3b80d8

tools/diagtool/CMakeLists.txt

@@ -17,6 +17,10 @@ add_clang_executable(diagtool
   ShowEnabledWarnings.cpp
 )
 
+add_dependencies(diagtool
+  ClangDiagnosticIndexName
+  )
+
 if(UNIX)
   set(CLANGXX_LINK_OR_COPY create_symlink)
 else()