This is equivalent to a change to grep.kak in 649e252f7 (bring *grep*
buffer to front in context of toolsclient, 2020-08-14).
If a toolsclient is set, make-next-error (and make-previous-error) will
jump to %opt{make_current_error_line}. This is wrong if the toolsclient
does not show the *make* buffer. In that case make_current_error_line
is undefined and we end up showing the goto menu. This has occasionally
been annoying me for a long time but I never bothered investigating.
Fix this by switching to the *make* buffer. The potential downside
is if make-next-error is run from the toolsclient, where we no longer
jump to the error but that's fine because we can use <ret>.
We can maybe improve this later by extending the logic, see
https://github.com/mawww/kakoune/pull/3656#pullrequestreview-472052285
As per man page eval(1p):
> The eval utility shall construct a command by concatenating arguments together,
> separating each with a `<space>` character. The constructed command shall be
> read and executed by the shell.
When not quoting `$kak_opt_makecmd` in the eval, the variable is split by
newlines and spaces and then joined by spaces to form the command. If there
were newlines in `$kak_opt_makecmd`, the command would be malformed.
To reproduce:
```kak
set-option global makecmd "
echo foo
echo bar"
make a b c
```
Expected output in the `*make*` buffer:
```
foo
bar a b c
```
Actual output:
```
foo echo bar a b c
```
This patch fixes this.
