The correct naming convention for RHEL is
    RHEL4_x86_64_gcc3_OPT.OBJ
    The makefiles were assuming that if the string 86 was found in uname -m
    it should use x86 for the arch.  However, it should only do this if
    uname -m is not x86_64.  Also, for RHEL/Linux, we do not have to add the
    NS64TAG just before the _OPT (or _DBG) since it's already in the arch.
    Other platforms continue to use the other naming convention.  The
    default naming convention for the mozilla components is
    Linux2.6_x86_64_glibc_PTH_64_OPT.OBJ.  I considered using Wan-Teh's
    instructions about source builds, but that would cause many changes to
    be made to our makefiles, so I just changed the way we calculate the
    mozilla OBJDIR name from the regular OBJDIR name.