Add nim package (#3748)

Nim is a statically typed compiled systems programming language.

Tested on ARM.

packages/nim.rb

+require 'package'
+
+class Nim < Package
+  description 'Nim is a statically typed compiled systems programming language.'
+  homepage 'https://nim-lang.org/'
+  version '1.0.4'
+  source_url 'https://nim-lang.org/download/nim-1.0.4.tar.xz'
+  source_sha256 '89841545a14475911bb84616bcd5a1b93a3268e1a6a0089f54642e405eeaaee0'
+
+  depends_on 'pcre'
+
+  def self.build
+    if ARCH == 'aarch64'
+      system 'sed -i "s,^ucpu=.*,ucpu=\"arm\"," build.sh'
+    end
+    system 'sh build.sh'
+    system 'bin/nim c koch'
+    system './koch tools'
+  end
+
+  def self.install
+    system 'sed -i "s,/usr/local,' + CREW_DEST_PREFIX + ',g" install.sh'
+    system "sh install.sh #{CREW_DEST_PREFIX}"
+  end
+end