Fix detection of C++ STL for tests.

Target tests weren't approrpiately using the libc++ gtest for
libc++_static, and the hosts tests were still using the old check.

Change-Id: I13813d5f09673b144b2dfead93eb81cb4bae0e34
diff --git a/core/target_test_internal.mk b/core/target_test_internal.mk
index 65def9c..50f4036 100644
--- a/core/target_test_internal.mk
+++ b/core/target_test_internal.mk
@@ -9,7 +9,7 @@
 my_test_libcxx := false
 ifndef LOCAL_SDK_VERSION
 ifeq (,$(TARGET_BUILD_APPS))
-ifeq ($(strip $(LOCAL_CXX_STL)),libc++)
+ifneq ($(filter $(strip $(LOCAL_CXX_STL)),libc++ libc++_static),)
 my_test_libcxx := true
 endif
 endif