Improve build system

- Reduce full build latency from ~20s to ~18s
- Bring back silent mode if `make V=0` is passed
- Demodernize utimes() polyfill so it works RHEL5
- Delete some old shell scripts that are no longer needed
- Truncate long lines when outputting builds to Emacs buffers

build/hello

@@ -0,0 +1,20 @@
+#!/bin/sh
+#-*-mode:sh;indent-tabs-mode:nil;tab-width:2;coding:utf-8-*-┐
+#───vi: set net ft=sh ts=2 sts=2 fenc=utf-8 :vi─────────────┘
+#
+# SYNOPSIS
+#
+#   HELLO BUILD
+#
+# OVERVIEW
+#
+#   We generate a line at the start of each Makefile run, because if we
+#   use `make V=0` mode then the terminal logging trick we use in
+#   tool/build/compile.c will delete the previous line, and we'd rather
+#   have that line not be the bash prompt that ran make.
+#
+#   This script is also useful for giving us an indicator each time the
+#   build restarts itself from scratch, which can happen in cases like
+#   when dependencies need to be regenerated by tool/build/mkdeps.c
+
+echo ♥cosmo >&2