Fix compile error on macOS introduced in r16111. n-i-bz.

Fix compile error on macOS introduced in r16111. n-i-bz.

m_syswrap/syswrap-generic.c:4148:26: error: use of undeclared identifier 'PID_EXEPATH'
      VG_(sprintf)(name, PID_EXEPATH, VG_(getpid)());
                         ^
m_syswrap/syswrap-generic.c:4150:56: error: use of undeclared identifier 'SELF_EXEPATH'
          && (VG_STREQ(arg1s, name) || VG_STREQ(arg1s, SELF_EXEPATH))) {
                                                       ^
m_syswrap/syswrap-generic.c:4150:56: error: use of undeclared identifier 'SELF_EXEPATH'
m_syswrap/syswrap-generic.c:4151:29: error: use of undeclared identifier 'SELF_EXEFD'
         VG_(sprintf)(name, SELF_EXEFD, VG_(cl_exec_fd));
                            ^

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@16116