abc: always write tmp files to TMPDIR

It is still possible to have it in CWD if TMPDIR is set to CWD.
The way it was is not ideal for logging purposes of large projects,
as this can create huge amounts of data best stored on some
scratch disk instead of the main drive.

passes/techmap/abc.cc

@@ -728,10 +728,7 @@ void abc_module(RTLIL::Design *design, RTLIL::Module *current_module, std::strin
 	po_map.clear();
 
 	std::string tempdir_name;
-	if (cleanup)
-		tempdir_name = get_base_tmpdir() + "/";
-	else
-		tempdir_name = "_tmp_";
+	tempdir_name = get_base_tmpdir() + "/";
 	tempdir_name += proc_program_prefix() + "yosys-abc-XXXXXX";
 	tempdir_name = make_temp_dir(tempdir_name);
 	log_header(design, "Extracting gate netlist of module `%s' to `%s/%s'..\n",