depend: remove script

Using the libgray approach the script is not needed anymore.
Instead of collecting all indirect dependencies of an object
(essentially redoing the work of the linker), we just link libgray.

This causes slightly more recompilations, but it's a lot simpler.

depend

@@ -1,30 +0,0 @@
-#!/bin/sh
-
-# Compute the dependencies (direct and transitive) of an object
-# This is used to collect all objects needed to link a program.
-
-# Bail out when .d files are missing
-test -f "${1%.o}.d" || exit 1
-
-# Check whether $1 contains substring $2
-contains(){ test "${1#*$2}" != "$1"; }
-
-# Walk the dependency graph (consisting of the set of all .d files)
-# and output the visited nodes (objects).
-walk_dag(){
-  while read -r line; do
-    # skip the first line (file own name)
-    contains "$line" ': ' && continue
-    # only look up object files
-    contains "$line" '.o ' || continue
-    line="${line% \\}"
-    contains "$visited" "$line" && continue
-    visited="$line:$visited"
-    printf '%s ' "$line"
-    # whether the node is a leaf
-    test "$(wc -l < "${line%.o}.d")" -gt 1 && walk_dag < "${line%.o}.d"
-  done
-}
-
-printf '%s ' "$1"  # the object itself
-walk_dag < "${1%.o}.d"