meson: add optdepends on sccache and ccache

[ognevny]

see https://mesonbuild.com/Feature-autodetection.html#ccache and https://mesonbuild.com/Release-notes-for-0-61-0.html#added-support-for-sccache

[ognevny]

any objections?

[Biswa96]

This not required in my opinion. One can install sccache/ccache and choose to use it without meson. Or, meson does not need sccache/ccache for general use cases.

[ognevny]

This not required in my opinion. One can install sccache/ccache and choose to use it without meson. Or, meson does not need sccache/ccache for general use cases.

that's why I added them to optdepends. I accidentally found that meson supports sccache without any extra options to be passed

[lazka]

fair enough I guess. It's just one of many things meson can use, but a very useful and easy to miss one. I've never used sccache though, only ccache.