I have ~x86 laptop and ~amd64 desktop, same problem. parser.cpp is generated from Makefile, using flex -i -8 -oparser.cpp encoding.l but declaration of parser.cpp is different than in /usr/include/unistd.h I know nothing about flex. I ctrl+z-ed emerge process and replaced parser.cpp, everything goes fine.
*** This bug has been marked as a duplicate of 122042 ***