ART: Extend bionic TLS use to host bionic

Use __BIONIC__ instead of ART_TARGET_ANDROID for bionic TLS usage.

Bug: 138329277
Test: m test-art-host
Test: art/test/testrunner/run_build_test_target.py art-linux-bionic-x64
Change-Id: I7dc605c6700323303d9c9503d3aecc4fddef8d45
diff --git a/runtime/thread-current-inl.h b/runtime/thread-current-inl.h
index 9241b1f..787ec5b 100644
--- a/runtime/thread-current-inl.h
+++ b/runtime/thread-current-inl.h
@@ -19,7 +19,7 @@
 
 #include "thread.h"
 
-#ifdef ART_TARGET_ANDROID
+#ifdef __BIONIC__
 #include <bionic_tls.h>  // Access to our own TLS slot.
 #endif
 
@@ -33,7 +33,7 @@
   if (!is_started_) {
     return nullptr;
   } else {
-#ifdef ART_TARGET_ANDROID
+#ifdef __BIONIC__
     void* thread = __get_tls()[TLS_SLOT_ART_THREAD_SELF];
 #else
     void* thread = pthread_getspecific(Thread::pthread_key_self_);