add syncthing package

packages/syncthing.rb

+require 'package'
+
+class Syncthing < Package
+  description 'An application that lets you synchronize your files across multiple devices'
+  homepage 'https://github.com/syncthing/syncthing'
+  version '0.14.40'
+  source_url 'https://github.com/syncthing/syncthing/archive/v0.14.40.tar.gz'
+  source_sha256 'b9820dceb472531f20ebd18ab53a66876970c9d78d22c93ff53c3c879363d6be'
+
+  binary_url ({
+  })
+  binary_sha256 ({
+  })
+
+  depends_on 'go' => build
+
+  def self.build
+    #The system tmp dir is mounted noexec, and the build will fail if it is used
+    system "TMPDIR=/usr/local/tmp go run build.go -version v0.14.40"
+  end
+
+  def self.install
+    system "mkdir -p #{CREW_DEST_PREFIX}/bin"
+    system "mv bin/syncthing #{CREW_DEST_PREFIX}/bin"
+    #The build process leaves 50M of files around that we do not need
+    system "rm -rf /usr/local/tmp/syncthing-*/"
+  end
+end