create-android-project.sh throws a warning on OSX because of uname -o parameter

cocos2d-x C++
#1

The uname executable for OSX does not recognize the o parameter and results in a warning when creating a new Android project:
<pre>
./create-android-project.sh
uname: illegal option — o
usage: uname
./create-android-project.sh: line 23: [: =: unary operator expected
</pre>
The manpage for uname states for theo parameter: _This is a synonym for the s option, for compatibility with other systems._
Therefore, we can safely use thes parameter or just ditch it altogether since -s seems to be the default.

#2

o is the flag left for cygwin, otherwise build_native.sh cannot work correctly on windows + cygwin.
I’m not sure ifs can do on cygwin since I have no the environment.
Ming can check this tomorrow.

Add chmod u+x $APP_DIR/android/build_native.sh is a good idea!

Thanks for your pull request! Please fix the commented NDK_ROOT & ANDROID_SDK_ROOT, and re-pull again.

#3

Done. Thanks!