Gash [ https://savannah.nongnu.org/projects/gash ] is a work-in-progress implementation of a POSIX shell in Scheme, that is already capable-enough to interpret Autoconf-generated configure scripts. It can run on Guile but it is designed to also run on Mes, meaning that we can use it early on during bootstrap.
The stage0 [ https://savannah.nongnu.org/projects/stage0 ] project by Jeremiah Orians starts everything from ~512 bytes; virtually nothing. Have a look at this incredible project if you haven’t already done so.
They're doing God's work!