[cmake] Fixes to build on Silicon

[simogasp]

Here are some fixes to build on Apple Silicon. They are mostly version bumps of the dependencies that have added support for the Silicon platform.

• bump geogram v1.7.6 -> v1.7.9
• bump png v1.6.35 -> 1.6.37
• some cmake adjustments to be platform independent

There are also some other bumps that I did not push yet:

• Tbb 2019_U6 -> v2021.3.0. It normally works, even for CCTag using the oneAPI branch (TBB:2021 oneAPI compatibility CCTag#178). But I don't know if there were other reasons for keeping the previous version
• for suitesparse no bump needed but for some reason I had to remove CC=${CMAKE_C_COMPILER} CXX=${CMAKE_CXX_COMPILER} from its build command line

[p12tic]

I think this can be set to PNG_ARM_NEON=on. The build without the flag fails because it tries to enable png NEON detection which is not portable and relies on user-supplied code which we don't have.

[simogasp]

And setting it to on when building on UNIX does not give problems?

[p12tic]

You're right, I missed that this is common code with x86.

[simogasp]

so maybe have a variable set like

if(${CMAKE_SYSTEM_PROCESSOR} MATCHES "arm") 
    set(AV_PNG_ARM_NEON on)
else()
    set(AV_PNG_ARM_NEON off)
endif()

so we can put -DPNG_ARM_NEON=${AV_PNG_ARM_NEON}
What do you think?

[p12tic]

That would make sense. I didn't suggest it because there're issues with CMAKE_SYSTEM_PROCESSOR - https://gitlab.kitware.com/cmake/cmake/-/issues/22881. Thinking about this more I think we should be safe with your approach because if the detection fails then we'll just use set(AV_PNG_ARM_NEON off).

[p12tic]

LGTM, I pretty much had to implement the same fixes in my own builds scripts that don't use ExternalProject_ADD.