GNU make 4.4 now uses a fifo for the jobserver

tool/lib/test/unit.rb

@@ -286,10 +286,15 @@ module Test
         @jobserver = nil
         makeflags = ENV.delete("MAKEFLAGS")
         if !options[:parallel] and
-          /(?:\A|\s)--jobserver-(?:auth|fds)=(\d+),(\d+)/ =~ makeflags
+          /(?:\A|\s)--jobserver-(?:auth|fds)=(?:(\d+),(\d+)|fifo:(.*))/ =~ makeflags
           begin
-            r = IO.for_fd($1.to_i(10), "rb", autoclose: false)
-            w = IO.for_fd($2.to_i(10), "wb", autoclose: false)
+            if fifo = $3
+              r = File.open(fifo, IO::RDONLY|IO::NONBLOCK|IO::BINARY, autoclose: false)
+              w = File.open(fifo, IO::WRONLY|IO::NONBLOCK|IO::BINARY, autoclose: false)
+            else
+              r = IO.for_fd($1.to_i(10), "rb", autoclose: false)
+              w = IO.for_fd($2.to_i(10), "wb", autoclose: false)
+            end
           rescue
             r.close if r
             nil