Re: LOCALBASE searched before macOS framework with CMake on Darwin

[triaxx%NetBSD.org@localhost]

> > If graphics/MesaLib is *not* installed:
> >
> >     % ~/pkg/sbin/pkg_info | grep MesaLib
> >
> > I understand that Cmake finds the OpenGL framework provided by macOS:
> >
> >     % grep "OPENGL_gl_LIBRARY:" work/openttd-14.0/cmake-pkgsrc-build/CMakeCache.txt
> > OPENGL_gl_LIBRARY:FILEPATH=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.2.sdk/System/Library/Frameworks/OpenGL.framework
> >
> > But if graphics/MesaLib is installed (but its buildlink3.mk is not the Makefile):
> >
> >     % ~/pkg/sbin/pkg_info | grep MesaLib
> >     MesaLib-21.3.9nb4   Open source OpenGL implementation
> >
> > Now Cmake finds the OpenGL implementation provided by pkgsrc:
> >
> >     % grep "OPENGL_gl_LIBRARY:" work/openttd-14.0/cmake-pkgsrc-build/CMakeCache.txt
> >     OPENGL_gl_LIBRARY:FILEPATH=/Users/triaxx/pkg/lib/libGL.dylib
> >
> > And the build step fails with the following error message:
> >
> >     ld: library 'GL' not found
> >     clang: error: linker command failed with exit code 1 (use -v to see invocation)
> >
> > What is the right way to avoid CMake finding OpenGL path in LOCALBASE first?
>
> MesaLib should not be installed on macOS at all. Just add something like:
>
> .if ${OPSYS} != "Darwin"
> .include "../../graphics/MesaLib/buildlink3.mk"
> .endif
>
> Kind regards,
> Adam

Actually, games/openttd has:

.if ${OPSYS} != "Darwin"
.include "../../devel/SDL2/buildlink3.mk"
.endif

and SDL deals with OpenGL for other Unix-like.

The problem here is that success or failure of the build process of 
games/openttd on Darwin depends on the installation of graphics/MesaLib 
while games/openttd doesn't include graphics/MesaLib/buildlink3.mk.

I think there is a problem with the CMake logic which should not look at 
LOCALBASE build in BUILDLINK_DIR to find dependency but (i) I am not 
sure and (ii) I have no idea how it could be fixed.

If graphics/MesaLib should not be installed on macOS, maybe could we add 
NOT_FOR_PLATFORM= Darwin in graphics/MesaLib/Makefile. But I see Darwin 
dedicated test for install step in this file...