pkgtools/pkglint: don't access the internet during the build

Pkglint needs goyacc, which is provided by devel/go-tools. But that
packages pulls in a lot of dependencies that are not needed for pkglint.
This includes a Perl interpreter and various cryptography packages.

Instead, during build, pkglint installs the only needed tool of that
collection (goyacc).

Since go-package.mk assumes that each pkgsrc package only downloads and
installs a single project, but pkglint now needs two of them (goyacc and
pkglint), most parts of go-package.mk had to be copied here and
implemented directly.


(rillig)

$NetBSD: distinfo,v 1.1 2018/11/10 11:42:23 rillig Exp $

SHA1 (tools-92d8274bd7b8a4c65f24bafe401a029e58392704.tar.gz) = 6d8999e8a535d7fcb40f64276dce3c525bebd7be
RMD160 (tools-92d8274bd7b8a4c65f24bafe401a029e58392704.tar.gz) = 79c3ef6bf7e941b6eee564023bb109247eea307d
SHA512 (tools-92d8274bd7b8a4c65f24bafe401a029e58392704.tar.gz) = 92027f221aa802798fd9734ebfc020163ccded95f6f2b208f614f45d8eec4f988ad77b155330fe8933ba3ddefe65af961a808b515a9b48da381b31da4f0d04bf
Size (tools-92d8274bd7b8a4c65f24bafe401a029e58392704.tar.gz) = 2741721 bytes