Update build instructions for the clang-format VS plugin

llvm-svn: 214529

Author: zmodem

clang/tools/clang-format-vs/README.txt

@@ -6,8 +6,11 @@ Build prerequisites are:
 - Visual Studio 2010 Professional
 - Visual Studio 2010 SDK.
 
-clang-format.exe must be copied into the ClangFormat/ directory before building.
-It will be bundled into the .vsix file.
+The extension is built using CMake by setting BUILD_CLANG_FORMAT_VS_PLUGIN=ON
+when configuring a Clang build, and building the clang_format_vsix target.
 
-The extension can be built manually from ClangFormat.sln (e.g. by opening it in
-Visual Studio), or with cmake by setting the BUILD_CLANG_FORMAT_VS_PLUGIN flag.
+The CMake build will copy clang-format.exe and LICENSE.TXT into the ClangFormat/
+directory so they can be bundled with the plug-in, as well as creating
+ClangFormat/source.extension.vsixmanifest. Once the plug-in has been built with
+CMake once, it can be built manually from the ClangFormat.sln solution in Visual
+Studio.