Link libc++demangle with libc++ for the device.

libc++demangle provides __cxa_demangle, which used to be a part of
libc++.so but is being moved out to save on resources since very few
libraries need it.

Test: make checkbuild
Bug: http://b/138245375
Change-Id: I677006dbbe87ccf2dd4df182114d2a6b985e3c00

core/cxx_stl_setup.mk

@@ -84,6 +84,7 @@ ifneq ($(filter $(my_cxx_stl),libc++ libc++_static),)
         my_ldflags += -nodefaultlibs
         my_cxx_ldlibs += $($($(my_prefix)OS)_$(my_link_type)_gcclibs)
     else
+        my_static_libraries += libc++demangle
         ifeq (arm,$($(my_prefix)$(LOCAL_2ND_ARCH_VAR_PREFIX)ARCH))
             my_static_libraries += libunwind_llvm
             my_ldflags += -Wl,--exclude-libs,libunwind_llvm.a