fm-simplex-plugin.1.01 uses autoconf

[emillon]

In #24013:

#=== ERROR while compiling fm-simplex-plugin.1.01 =============================#
# context              2.2.0~alpha~dev | linux/x86_64 | ocaml-base-compiler.4.14.1 | file:///home/opam/opam-repository
# path                 ~/.opam/4.14/.opam-switch/build/fm-simplex-plugin.1.01
# command              ~/.opam/opam-init/hooks/sandbox.sh build make fm-simplex
# exit-code            2
# env-file             ~/.opam/log/fm-simplex-plugin-7-a7c8da.env
# output-file          ~/.opam/log/fm-simplex-plugin-7-a7c8da.out
### output ###
# autoconf
# make: autoconf: No such file or directory
# Makefile.users:259: .depend: No such file or directory
# make: *** [Makefile.users:370: configure] Error 127

[mseri]

Still will not build in many cases since it requires alt-ergo 1.01 that does:

# mkdir -p /usr/local/bin
# cp -f alt-ergo.opt /usr/local/bin/alt-ergo
# cp: cannot create regular file '/usr/local/bin/alt-ergo': Read-only file system