tricore-debian-cross-container CI job failing

[Peter Maydell]

The tricore-debian-cross-container CI job has started failing for
no obvious reason:

https://gitlab.com/qemu-project/qemu/-/jobs/3593581274

gcc -DHAVE_CONFIG_H -I. -I. -I. -D_GNU_SOURCE -I. -I. -I../bfd
-I./../bfd -I./../include -I./../intl -I../intl -w
-DLOCALEDIR="\"/usr/local/share/locale\"" -W -Wall -Wstrict-prototypes
-Wmissing-prototypes -w -c `test -f 'ldgram.c' || echo './'`ldgram.c
`test -f ldlex.l || echo './'`ldlex.l
/bin/sh: 1: ldlex.l: not found

I think this is happening because the makefile thinks it needs to
rebuild the ldlex.c file but doesn't know how to. In turn this
is probably because:
(a) we don't install flex or bison in the container that's doing
this binutils build

(b) the binutils sources we're building are confused, because they
have a 'missing' script that is not compatible with the 'configure',
and so configure warns:

/usr/src/binutils/missing: Unknown `--run' option
Try `/usr/src/binutils/missing --help' for more information
configure: WARNING: `missing' script is too old or missing

and then later in the build when it needs to do something to
handle the "I have no 'flex' or 'bison'" code path it fails
obscurely rather than being able to use the 'missing' script to
deal with it.

https://stackoverflow.com/questions/40962711/configure-warning-missing-script-is-too-old-or-missing
suggests that this can happen if some autotools stuff wasn't
done right or not all the files were checked into the repo.

I dunno how easy that is to fix. Perhaps installing flex
and bison in our container might be easiest.

thanks
-- PMM