emit_rerun_if_changed piped protoc output through /dev/stdout and
/dev/null, which do not exist on Windows — the release build's Windows
job failed there even with protoc on PATH. Both protoc outputs now go
to real files under the build script's OUT_DIR (deterministic names, so
reruns overwrite), the dependency list is read from disk, and the
make-style target prefix is matched with normalized path separators
since protoc may spell the target with forward slashes on Windows.
Verified locally by forcing a fresh build-script run: the .d file lands
in OUT_DIR and kigi-tools-api builds cleanly.
ZacharyZhang-NY
641c73899c