Update gyp script to adapt new Android 20 name

We were using "??.0.0" to match android sdk tool path, e.g. "18.0.0",
"19.0.0". Now android 20 is using another name - "android-4.4W"
So we need to change the matching pattern accordingly.

BUG=https://crosswalk-project.org/jira/browse/XWALK-2117
Merge pull request #5 from deqing/newsdk

Update gyp script to adapt new Android 20 name