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/objdump

@@ -1,22 +0,0 @@
-#!/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─────────────┘
-#
-# OVERVIEW
-#
-#   GNU Disassembly Veneer
-#
-# DESCRIPTION
-#
-#   This script wraps normal objdump commands that're transparently
-#   passed-through.
-#
-# EXAMPLE
-#
-#   build/objdump -xd o/tiny/examples/life.com.dbg
-
-if [ ! -d o/third_party/gcc ]; then
-  third_party/gcc/unbundle.sh
-fi
-
-exec o/third_party/gcc/bin/x86_64-linux-musl-objdump "$@"