Without this, a "make all-sim" without the equivalent of
libreadline-dev installed on the build system, won't
properly pick up the in-tree readline build, and you'll see:

mkdir -p -- ./sim
Configuring in ./sim
configure: creating cache ./config.cache
checking build system type... x86_64-pc-linux-gnu
checking host system type... x86_64-pc-linux-gnu
checking target system type... cris-axis-elf
checking for x86_64-pc-linux-gnu-gcc... gcc
checking whether the C compiler works... yes
...
checking for library containing tgetent... -ltermcap
checking for readline in -lreadline... no
configure: error: the required "readline" library is missing
make[1]: *** [Makefile:11188: configure-sim] Error 1
make[1]: Leaving directory '/home/hp/sim/b'

The sim dependency on readline is apparently (nominally)
valid as there's a readline call in sim/erc32/sis.c.

2022-02-21  Hans-Peter Nilsson  <hp@axis.com>

	* Makefile.def (dependencies): Make configure-sim depend on
	all-readline.
	* Makefile.in: Regenerate.