build.dumb

#!/usr/bin/env dumb

in: fentry.cpp
out: fentry.o
cmd: clang++ -std=c++23 -ggdb3 -fPIC -mgeneral-regs-only -c fentry.cpp

in: count.cpp
out: count.o
cmd: clang++ -std=c++23 -ggdb3 -fPIC -c count.cpp

in: count.o fentry.o
out: count.so
cmd: clang++ -std=c++23 -ggdb3 -fPIC -shared -rdynamic count.o fentry.o -o count.so

in: user.cpp
out: user
cmd: clang++ -std=c++23 -ggdb3 -pg -mfentry user.cpp -o user

dumb

#!/bin/bash
check() {
    [[ ! -e $1 ]] && return
    for i in ${@:2}; do
        [[ $1 -ot $i ]] && return
    done
}
in: () { in=$*; }
out:() { out=$*; }
cmd:() {
    for i in $out; do
        if check $i $in; then
            echo cmd: $@
            $@ || { e=$?; rm -f $out; exit $e; }
            break
        fi
    done
}

for i do . $i; done