Yes, that would be best. Perhaps along the lines of:
;;;; bb.setup -*- Scheme -*-
(define has-flu? (zero? (system "flu-config --version")))
(make/proc
(list (list "bb-support.so" '("bb-support.cpp" "bb.h")
(lambda ()
(run (g++ -Os -fomit-frame-pointer -fPIC -c
,(if has-flu? "`flu-config --cflags` -DBB_USE_FLU" "")
"`fltk-config --cflags`" bb-support.cpp)) ) ) )
"bb-support.so")
(run (csc bb.scm -s -O2 -d0
-L "\"bb-support.o `fltk-config --use-images --use-gl --ldflags
--libs`\""
,(if has-flu? "-L \"`flu-config --ldflags --libs`" "")
-ld g++) )
(install-extension 'bb '("bb.so"))