Set the GYP_DEFINES environment variable when syncing dependencies

This closes #233

Author: ignisf

ext/libv8/builder.rb

@@ -110,15 +110,15 @@ def setup_build_deps!
       ENV['PATH'] = "#{File.expand_path('../../../vendor/depot_tools', __FILE__)}:#{ENV['PATH']}"
       Dir.chdir(File.expand_path('../../../vendor', __FILE__)) do
         unless Dir.exists? 'v8'
-          system "fetch v8" or fail "unable to fetch v8 source"
+          system "env #{gyp_defines} fetch v8" or fail "unable to fetch v8 source"
         else
-          system "gclient fetch" or fail "could not fetch v8 build dependencies commits"
+          system "env #{gyp_defines} gclient fetch" or fail "could not fetch v8 build dependencies commits"
         end
         Dir.chdir('v8') do
           unless system "git checkout #{source_version}"
             fail "unable to checkout source for v8 #{source_version}"
           end
-          system "gclient sync" or fail "could not sync v8 build dependencies"
+          system "env #{gyp_defines} gclient sync" or fail "could not sync v8 build dependencies"
           system "git checkout Makefile" # Work around a weird bug on FreeBSD
         end
       end

release/x86_64-freebsd-11/Vagrantfile

@@ -12,7 +12,7 @@ Vagrant.configure(2) do |config|
 
   # Every Vagrant development environment requires a box. You can search for
   # boxes at https://atlas.hashicorp.com/search.
-  config.vm.box = "freebsd/FreeBSD-11.0-RELEASE-p1"
+  config.vm.box = "freebsd/FreeBSD-11.0-STABLE"
 
   # Disable automatic box update checking. If you disable this, then
   # boxes will only be checked for updates when the user runs