Avoid using readPipeBlockingMulti (see clean-platform#53)

cleantest.icl

@@ -385,9 +385,12 @@ where
 
 		readPipes :: !*ProcessOutput !ProcessIO !*File !*World -> *(!MaybeOSError Bool, !*ProcessOutput, !*File, !*World)
 		readPipes output pio io w
-		# (ss,w) = readPipeBlockingMulti [pio.stdOut, pio.stdErr] w
-		| isError ss
-			# oserr=:(err,msg) = fromError ss
+		# (out,w) = readPipeBlocking pio.stdOut w
+		# (err,w) = readPipeNonBlocking pio.stdErr w
+		| isError out || isError err
+			# oserr=:(err,msg) = case out of
+				Error e -> e
+				_       -> fromError err
 			# event = Failed Nothing
 			# io = emit (EndEvent
 				{ name    = r.TestRun.name
@@ -395,7 +398,8 @@ where
 				, message = "Failed to read child process IO (" <+ err <+ "; " <+ msg <+ ")"
 				}) io
 			= (Error oserr, output, io, w)
-		# [out,err:_] = fromOk ss
+		# out = fromOk out
+		# err = fromOk err
 		# (output,(continue,io)) = append out
 			(\s (continue,io)
 				| not continue && opts.stop_on_first_failure