> Can you run ‘file’ on libgcc.a (or one of the .o files it contains)?
> Can you check in the glibc log whether a -mabi flag is passed?

Oh, I forgot to add the -K option.  There are no logs.

> You may need to explicitly add -mabi=64 for glibc.  It should be
> possible to do it with something like:

>   #:configure-flags '("CFLAGS=-mabi=64 -g -O2")

Which 'glibc' should be used?

I tried to use

       ((#:configure-flags flags)
        `(cons ,(string-append "CFLAGS=-mabi=64 -g -O2 " "--host=" target)
               ,flags))

in 'cross-libc' ('cross-base.scm'), but it failed:

checking for suffix of object files... configure: error: in `/tmp/nix-build-glibc-cross-mips64el-linux-gnu-2.17.drv-3/build':
configure: error: cannot compute suffix of object files: cannot compile

I reread the quasiquote-related part of the manual, but I still fail to
understand how to add 'CFLAGS' properly.