aapt: move qsort_r_compat here as it is sole client

This code is only used on the host for MacOS X compatibility.
Apparently, glibc and Apple's libc disagree on the parameter
ordering.

Change-Id: I214edcf2870b6ac88316306ac5af43f1dadf9b2e
Signed-off-by: Dima Zavin <dima@android.com>