cc -Wall -Werror -Wmissing-prototypes -I../posix_spawn -g -O2 
    -fsanitize=undefined -o cush -L../posix_spawn cush.o 
    shell-grammar.o list.o shell-ast.o termstate_management.o utils.o 
    signal_support.o -lspawn -ll -lreadline

/usr/bin/ld: cush.o: in function `main':
/..../cs3214-cush/src/cush.c:272: undefined reference to `job_list'
collect2: error: ld returned 1 exit status
make: *** [Makefile:27: cush] Error 1