add a "most" target, and make it the default

split out of https://codereview.appspot.com/6651064/ ('gyp: generate "everything" and "most" targets instead of "all"')
tests: "make most" now works, "make" now calls "make most"
Review URL: https://codereview.appspot.com/6740045

git-svn-id: http://skia.googlecode.com/svn/trunk@5999 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gyp_skia b/gyp_skia
index d6b5504..af08f07 100755
--- a/gyp_skia
+++ b/gyp_skia
@@ -88,6 +88,9 @@
   # Tell make to write its output into the same dir
   args.extend(['-Goutput_dir=.'])
 
+  # By default, we build 'most' instead of 'all' or 'everything'. See skia.gyp.
+  args.extend(['-Gdefault_target=most'])
+
   # Special arguments for generating Visual Studio projects:
   # - msvs_version forces generation of Visual Studio 2010 project so that we
   #   can use msbuild.exe