[Android] make_apk.py print exception message when search aapt.

If the environment value in Windows is PATHEXT=.COM;.EXE;blabla.
The Find(name, path) function will raise exception when match with ".com".
But actually. only aapt(Linux) and aapt.exe(Windows) is the result what we want.

BUG=https://crosswalk-project.org/jira/browse/XWALK-1906