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
diff --git a/runtime/runtime.cc b/runtime/runtime.cc
index 8a3bac7..ee4d669 100644
--- a/runtime/runtime.cc
+++ b/runtime/runtime.cc
@@ -2183,7 +2183,7 @@
 
 NO_RETURN
 void Runtime::Aborter(const char* abort_message) {
-#ifdef __ANDROID__
+#ifdef ART_TARGET_ANDROID
   android_set_abort_message(abort_message);
 #endif
   Runtime::Abort(abort_message);