Remove uses of libcxx.mk.

This is a no-op.

Change-Id: Ifc0d51d594011069ab80e6fc21603e10e720a5d2
diff --git a/keystore/Android.mk b/keystore/Android.mk
index eb9dd87..3480123 100644
--- a/keystore/Android.mk
+++ b/keystore/Android.mk
@@ -71,7 +71,6 @@
 ifeq ($(USE_32_BIT_KEYSTORE), true)
 LOCAL_MULTILIB := 32
 endif
-include external/libcxx/libcxx.mk
 LOCAL_CFLAGS := -Wall -Wextra -Werror
 LOCAL_SRC_FILES := auth_token_table.cpp
 LOCAL_MODULE := libkeystore_test
diff --git a/keystore/tests/Android.mk b/keystore/tests/Android.mk
index 6374896..be8c426 100644
--- a/keystore/tests/Android.mk
+++ b/keystore/tests/Android.mk
@@ -21,7 +21,6 @@
 ifeq ($(USE_32_BIT_KEYSTORE), true)
 LOCAL_MULTILIB := 32
 endif
-include external/libcxx/libcxx.mk
 LOCAL_CFLAGS := -Wall -Wextra -Werror
 LOCAL_SRC_FILES := auth_token_table_test.cpp
 LOCAL_MODULE := auth_token_table_test