use depfile in integrationtests

[YamasouA]

closes #649

This PR try to create dependencyfile and parse the file.

[YamasouA]

check script

#!/usr/bin/env bash
set -euo pipefail

# Target to watch
LD_OUT="wild/tests/build/rust-integration.rs-llvm-dynamic-host.ld"
SRC="wild/tests/sources/rust-integration.rs"

# mtime (nanoseconds)
mtime_ns() { python3 - "$1" <<'PY'
import os,sys; print(os.stat(sys.argv[1]).st_mtime_ns)
PY
}

# 1st run: expect full link
cargo clean
cargo test --test integration_tests -- --nocapture
t1=$(mtime_ns "$LD_OUT"); echo "t1=$t1"

# 2nd run: no changes -> expect ld skip (mtime unchanged)
cargo test --test integration_tests -- --nocapture
t2=$(mtime_ns "$LD_OUT"); echo "t2=$t2"

if [[ "$t1" != "$t2" ]]; then
  echo "NG: mtime changed on 2nd run (= ld ran)"
  exit 1
else
  echo "OK: mtime unchanged on 2nd run (= ld skipped)"
fi

# 3rd run: touch only the relevant source -> expect relink (mtime changes)
sleep 1                       # cross the second boundary as a safety margin
touch "$SRC"
sleep 1                       # avoid running immediately

cargo test --test integration_tests -- --nocapture
t3=$(mtime_ns "$LD_OUT"); echo "t3=$t3"

if [[ "$t2" == "$t3" ]]; then
  echo "NG: mtime unchanged after touching source (= ld did not run)"
  exit 1
else
  echo "OK: mtime changed after touching source (= ld relinked)"
fi

[lapla-cogito]

Thanks for working on this!

[YamasouA]

@lapla-cogito
Thank you for your quick review.
I fix your comment.

[davidlattimore]

Thanks for doing this!