Allow overriding the compile SDK

We automatically pull the compile SDK from the platform. But,
in certain circumstances the platform's SDK codename is
incorrect. Allow the name to be overridden on the command line.

Change-Id: I398f1b00b29db42e4ce202b94cda483c98971a14
Fixes: 78324052
Test: ./out/host/linux-x86/nativetest64/aapt2_tests/aapt2_tests