Use environment tempdir variable for parallel IPC directory

Author: kpaulisse

lib/octocatalog-diff/util/parallel.rb

@@ -6,6 +6,7 @@
 # this instead executes the tasks serially, but provides the same API as the parallel tasks.
 
 require 'stringio'
+require_relative 'util'
 
 module OctocatalogDiff
   module Util
@@ -107,14 +108,14 @@ def self.run_tasks(task_array, logger = nil, parallelized = true, raise_exceptio
       # @return [Exception] First exception encountered by a child process; returns nil if no exceptions encountered.
       def self.run_tasks_parallel(result, task_array, logger)
         pidmap = {}
-        ipc_tempdir = Dir.mktmpdir('ocd-ipc-')
+        ipc_tempdir = OctocatalogDiff::Util::Util.temp_dir('ocd-ipc-')
 
         # Child process forking
         task_array.each_with_index do |task, index|
           # simplecov doesn't see this because it's forked
           # :nocov:
           this_pid = fork do
-            ENV['OCTOCATALOG_DIFF_TEMPDIR'] = ipc_tempdir
+            ENV['OCTOCATALOG_DIFF_TEMPDIR'] ||= ipc_tempdir
             task_result = execute_task(task, logger)
             File.open(File.join(ipc_tempdir, "#{Process.pid}.dat"), 'w') { |f| f.write Marshal.dump(task_result) }
             Kernel.exit! 0 # Kernel.exit! avoids at_exit from parents being triggered by children exiting