Fix the target Linux builds of ART

When ART_TARGET_LINUX was set it would hit some pieces of dead code that
were using old defines i.e. `__ANDROID__`

Test: export ART_TARGET_LINUX=true
Test: source build/envsetup.sh
Test: lunch
Test: cd art && mma

Change-Id: I80102750192928606e0884d2b723a87ccb7d7e19