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: Ie97225d496d7d40f8749522bf36702a2d9dcdfe7