Hi,

[…]

> * gnu/packages/games.scm (knights):
> [make-flags] add "CXXFLAGS=-lpthread"

Rather:
* gnu/packages/games.scm (knights)[arguments]<#:make-flags>: Add
"CXXFLAGS=-lpthread".

> ---
>  gnu/packages/games.scm | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/gnu/packages/games.scm b/gnu/packages/games.scm
> index cff1c0af99..dc0511e55a 100644
> --- a/gnu/packages/games.scm
> +++ b/gnu/packages/games.scm
> @@ -1366,7 +1366,8 @@ built-in level editor.")
>      (build-system gnu-build-system)
>      (arguments
>       '(#:make-flags
> -       (list (string-append "PREFIX=" (assoc-ref %outputs "out")))
> +       (list (string-append "PREFIX=" (assoc-ref %outputs "out"))
> +	     "CXXFLAGS=-lpthread")

^
Please, use spaces instead of tabs. ;-)

>         #:phases
>         (modify-phases %standard-phases
>           ;; No configure script.

Pushed to master with mentioned changes.

Oleg.