I tried to run cl-launch with mkcl, and mkcl crashed during the
upgrade of asdf from 3.0.3.0.1 to 3.1.2:
echo '(in-package :fare-quasiquote) (format t "~A~%" *package*)' | cl
-l mkcl -s fare-quasiquote-extras -f -
Error during command line arguments processing:
                           The index 35 (max: 31) is not a valid slot
index in the object #<ASDF/SYSTEM:SYSTEM "asdf">..

I suppose it's the new slots added in the syntax-control branch that
are confusing mkcl when it fails to correctly use the magic that calls
update-instance-for-redefined-class.

I tried to compile a newer mkcl with asdf 3.1.2, but got this error:

make[2]: Leaving directory `/home/tunes/src/common-lisp/mkcl/src/c'
gcc  -o mkcl_min c/cinit.o c/all_symbols.o mkclmin.a mkclgc.a -lgmp
-pthread -lrt -ldl  -lm
mkclmin.a(alloc_2.o): In function `mkcl_init_alloc':
/home/tunes/src/common-lisp/mkcl/src/c/alloc_2.d:1007: undefined
reference to `MK_GC_set_thr_restart_signal'
mkclmin.a(unixint.o): In function `mkcl_init_late_unixint':
/home/tunes/src/common-lisp/mkcl/src/c/unixint.d:1918: undefined
reference to `MK_GC_get_thr_restart_signal'
collect2: ld returned 1 exit status