Update GN docs about Visual Studio generators

tools/gn/docs/faq.md

 # GN Frequently Asked Questions
 
 [TOC]
 
 ## How will the build be converted?
 
 We intend to build a second independent build in parallel to the GYP
 build. Previous efforts to generate GYP as an intermediate stage proved
 difficult. There will be some smaller set of bots compiling this build,
 and we'll keep the GN build running on these configurations.
@@ skipping 13 matching lines @@
 
 Since common.gypi is not used for GN-generated GYP files, any rules
 there will no longer apply. There is a _lot_ of logic in there for many
 build configurations and various conditions where certain flags should
 or should not be used. Some of these build configurations aren't even
 supported any more. Some are run on other waterfalls or are used by
 individuals manually setting GYP\_DEFINES on their local system.
 
 ## Will XCode/Visual Studio still be supported?
 
-They're not supported now.
+Visual Studio is supported. Visual Studio can be used as an IDE for code
+browsing or debugging but Ninja is used for building.
+Run `gn help gen` for more details.
 
-Long-term, if your use-case is to use Ninja for building but Visual
-Studio or XCode for debugging, there is desire to write a simple wrapper
-around Ninja that lists the files in Visual Studio or XCode format, and
-has a command to run ninja for when you press build. This setup should
-provide the type of interactive debugging experience people want (the
-iOS team currently uses a Ninja/XCode build like this with success).
-
-This project is not staffed. If you're interested, it probably isn't too
-hard. It won't get done unless somebody volunteers. There is a [spec for
-IDE
-integration](https://docs.google.com/document/d/1kwREU99u8GpRammLbbKwrfaDI6WV7nsMAaoF5dcuhOU/edit?usp=sharing).
+XCode is not supported yet. We need help!
 
 ## I'm weird. Will my uncommon build mode be supported?
 
 One of the main benefits of the build changeover is that it will
 encourage us to refactor the build system. The project has generally not
 been as strict with build complexity and maintenance as we have with
 source code, and a lot of cruft has accumulated.
 
 In most cases, we will want to rethink how build flags are supported. We
 want to be more modular rather than throwing everything in the
@@ skipping 55 matching lines @@
     `is_official_build = true`
   * The default is Chromium branding. To do Chrome branding, set
     `is_chrome_branded = true`
 
 ## How do I do cross-compiles?
 
 GN has robust support for doing cross compiles and building things for
 multiple architectures in a single build.
 
 See [GNCrossCompiles](cross_compiles.md) for more info.