Remove skia_arch_width, fold into skia_arch_type.

site/user/quick/linux.md

 Linux
 =====
 
 Quickstart
 ----------
 
 1.  Install depot tools.
 
     <!--?prettify lang=sh?-->
 
@@ skipping 76 matching lines @@
     ./gyp_skia
 
 Or, you can just rely on it being run automatically by using `make` instead of
 `ninja` in examples shown below.
 
 If you want to use Eclipse, see Creating an Eclipse Project after you have generated the makefiles.
 
 On 32-bit Linux (when `uname -m` is *not* `x86_64`), you will have to
 explicitly specify the architecture:
 
-    GYP_DEFINES='skia_arch_width=32' ./gyp_skia
+    GYP_DEFINES='skia_arch_type=x86' ./gyp_skia
 
 Build and run tests from the command line
 -----------------------------------------
 
     ninja -C out/Debug dm
     out/Debug/dm
 
 The usual mode you want for testing is Debug mode (`SK_DEBUG` is defined, and
 debug symbols are included in the binary). If you would like to build the
 
@@ skipping 54 matching lines @@
 Build tools
 -----------
 
     make -j tools
     out/Debug/skdiff
 
 Clean up all generated files
 ----------------------------
 
     make clean