Remove use of external/vixl/src in include_dirs

The include_dirs property is deprecated and no longer needed as the
libvixl[d] libraries export their include dirs directly.

Added support to the codegen extensions to allow header include dirs
from libvixl[d] to be re-exported from libart-compiler[d] as the
latter's exported headers include vixl exported headers.

Test: m checkbuild
Bug: 134379140
Change-Id: I6ad47b093cc25fc1486109fced1c2a238e75ff0d
3 files changed