Bug#951281: widelands FTBFS: SDL2_INCLUDE_DIR-NOTFOUND

[Simon McVittie]

Control: affects 951087 + src:widelands

On Sat, 15 Feb 2020 at 10:49:59 +0200, Juhani Numminen wrote:
> I think the error is actually this (abridged):
> 
> -- SDL2_INCLUDE_DIR is SDL2_INCLUDE_DIR-NOTFOUND
...
> The trigger to breaking cmake/Modules/FindSDL2.cmake in widelands is
> libsdl2 2.0.10+dfsg1-2, it seems. The attached patch fixes this FTBFS.

This regression in libsdl2 is <https://bugs.debian.org/951087>. I have
proposed a solution, with an autopkgtest.

If you are going to work around this in widelands by changing how the
upstream code finds SDL2, instead of making changes to the FindSDL2 module
(which has no real upstream and gets copy/pasted between projects like
the macros that give Autoconf a bad name), I think it would be better to
rely on SDL2 >= 2.0.4 having full CMake integration. Something like this,
which I recently uploaded and proposed upstream:
https://salsa.debian.org/games-team/openjk/commit/22fd18c4f2fb01bce65bc8737536c123c5f4bceb

    smcv