Use :if-feature for the entire system, and invoke ccl with --no-init.
-rw-r--r-- 33 .gitignore
-rw-r--r-- 2468 README
-rw-r--r-- 154 build.xcvb
-rwxr-xr-x 260 make-single-threaded-ccl.lisp
-rw-r--r-- 855 single-threaded-ccl.asd
-rw-r--r-- 1619 single-threaded-ccl.lisp