cmake: Use compatibility list in source directory

[nezd5553]

For Flatpak builds, the compatibility list is located in the source directory, because the Flatpak build system is not allowed access to the internet. In this case, CMake will copy it to ${PROJECT_BINARY_DIR}/dist/compatibility_list/. This fixes the issue in the Flatpak build where the compatibility of all games is "not tested" as mentioned in flathub/org.yuzu_emu.yuzu#6.

[Docteh]

I think there should be a comment explaining the section, maybe even a link to https://github.com/flathub/org.yuzu_emu.yuzu if you're feeling generous

putting the compatibility list into dist/compatibility_list/ on the ${PROJECT_SOURCE_DIR} side might also be good idea.

# the flatpak build provides its own copy of compatibility list as the flatpak build system is 
# not allowed internet access. flatpak is at https://github.com/flathub/org.yuzu_emu.yuzu