fix incompatibility with -fstack-protector-strong

The __libc_init_tls function in libc_init_common.cpp takes a reference
to a local variable so it ends up being protected. Since this happens
before TLS and the stack guard value are initialized, it breaks.

The libc_init_common code needs to be compiled with -fno-stack-protector
and can then be merged into libc_bionic.

Change-Id: Ie95ea2ff533d4af1cfad1c9bc59e49f20a8e119d