Redirect links to faster-builds tips to newly merged Linux instructions

The tips on faster Linux builds got merged into the general Linux build
instructions. But there were a couple of links to the now-deleted old tips
page.

I've added a named anchor inside the merged instructions and redirected one
link there. The other link was a self-link and I removed it.

BUG=

Review-Url: https://codereview.chromium.org/2554803003
Cr-Commit-Position: refs/heads/master@{#437141}

docs/common_build_tasks.md

@@ -56,7 +56,8 @@ building release mode with DCHECKs enabled using the following define:
 
 ### Linux
 
-Linux has its own page on [making the build faster](linux_faster_builds.md).
+The Linux build instructions page has its own section on [making the build
+faster](linux_build_instructions.md#faster-builds).
 
 ## Configuring the Build
 

docs/linux_build_instructions.md

@@ -117,7 +117,7 @@ $ gn gen out/Default
 * For more info on GN, run `gn help` on the command line or read the
   [quick start guide](../tools/gn/docs/quick_start.md).
 
-### Faster builds
+### <a id=faster-builds></a>Faster builds
 
 This section contains some things you can change to speed up your builds,
 sorted so that the things that make the biggest difference are first.
@@ -137,9 +137,6 @@ By default GN produces a build with all of the debug assertions enabled
 line-by-line debugging. Setting `symbol_level=0` will include no debug
 symbols at all. Either will speed up the build compared to full symbols.
 
-See [faster builds on Linux](linux_faster_builds.md) for various tips and
-settings that may speed up your build.
-
 #### Disable debug symbols for Blink
 
 Due to its extensive use of templates, the Blink code produces about half