Linker --wrap option resolves to __wrap_symbol for undefined symbol.
During the compilation of host libportable.a, __HOST__ is defined
to rename all portable functions to __wrap_symbol, and the
real function to __real_symbol. This way libportable.a can be
validated at host w/o changes of user's source code.
See http://sourceware.org/binutils/docs/ld/Options.html
Change-Id: Idcbe53dd642536f3dc2be85a875f95535b9dc0b1
