Buffer stderr and stdout before triggering callbacks

Currently, whenever the compile_command outputs data on stdout or stderr
the corresponding on_stdout or on_stderr is called. This results in
multiple (at least 5 for even one compilation error) calls to those
functions which in turn do some work parsing errors. Adding
stdout_buffered and stderr_buffered to jobstart will wait until they
finish writing to those descriptors, reducing the calls to on_stdout and
on_stderr to at most one.

lua/compile-mode/init.lua

@@ -145,7 +145,9 @@ local runjob = a.wrap(function(cmd, bufnr, param, callback)
 	log.debug("starting job...")
 	local job_id = vim.fn.jobstart(cmd, {
 		cwd = vim.g.compilation_directory,
+		stdout_buffered = true,
 		on_stdout = on_either,
+		stderr_buffered = true,
 		on_stderr = on_either,
 		on_exit = function(id, code)
 			callback(count, code, id)