Update Linux build docs to remove GYP references.

docs/linux_faster_builds.md

 # Tips for improving build speed on Linux
 
 This list is sorted such that the largest speedup is first; see
 [Linux build instructions](linux_build_instructions.md) for context and
 [Faster Builds](common_build_tasks.md) for non-Linux-specific techniques.
 
 [TOC]
 
 ## Use goma
 
@@ skipping 48 matching lines @@
 
 ## Linking
 
 ### Dynamically link
 
 We normally statically link everything into one final executable, which produces
 enormous (nearly 1gb in debug mode) files. If you dynamically link, you save a
 lot of time linking for a bit of time during startup, which is fine especially
 when you're in an edit/compile/test cycle.
 
-Run gyp with the `-Dcomponent=shared_library` flag to put it in this
-configuration.  (Or set those flags via the `GYP_DEFINES` environment variable.)
-
-e.g.
-
-    build/gyp_chromium -D component=shared_library
-    ninja -C out/Debug chrome
+Add the flag `is_component_build=true` in your build args (to edit build args
+run `gn args out/foo` where `out/foo` is your build directory).
 
 See the
 [component build page](http://www.chromium.org/developers/how-tos/component-build)
 for more information.
 
 ### Linking using gold
 
 The experimental "gold" linker is much faster than the standard BFD linker.
 
 On some systems (including Debian experimental, Ubuntu Karmic and beyond), there
@@ skipping 10 matching lines @@
 
 ## WebKit
 
 ### Build WebKit without debug symbols
 
 WebKit is about half our weight in terms of debug symbols. (Lots of templates!)
 If you're working on UI bits where you don't care to trace into WebKit you can
 cut down the size and slowness of debug builds significantly by building WebKit
 without debug symbols.
 
-Set the gyp variable `remove_webcore_debug_symbols=1`, either via the
-`GYP_DEFINES` environment variable, the `-D` flag to gyp, or by adding the
-following to `~/.gyp/include.gypi`:
-
-```
-{
-  'variables': {
-    'remove_webcore_debug_symbols': 1,
-  },
-}
-```
+Set the GN build arg `remove_webcore_debug_symbols=true` (to edit build args
+run `gn args out/foo` where `out/foo` is your build directory).
 
 ## Tune ccache for multiple working directories
 
 (Ignore this if you use goma.)
 
 Increase your ccache hit rate by setting `CCACHE_BASEDIR` to a parent directory
 that the working directories all have in common (e.g.,
 `/home/yourusername/development`). Consider using
 `CCACHE_SLOPPINESS=include_file_mtime` (since if you are using multiple working
 directories, header times in svn sync'ed portions of your trees will be
@@ skipping 32 matching lines @@
 or for a release build.
 ***
 
 Quick and dirty benchmark numbers on a HP Z600 (Intel core i7, 16 cores
 hyperthreaded, 12 GB RAM)
 
 *   With tmpfs:
     *   12m:20s
 *   Without tmpfs
     *   15m:40s