Just had to deal with same problem today, so if someone else bumps into this question: some file extensions are missing. Something like works fine:
SECTIONS
{
.text : { libxyz.a:abc.o(.text) }
.data : { libxyz.a:abc.o(.data) }
.bss : { libxyz.a:abc.o(.bss) }
}
One also needs to deal with paths (if library is actually somewhere/libxyz.a).