Add Linux definition to build

[rhaamo]

Duplicate and edit the APPLE line for LINUX to build.
Related to opentoonz/opentoonz_plugin_utility#4 since opentoonz_plugin_utility is a submodule.
Actually it builds and OpenToonz doesn't seems to cry at startup.
I haven't checked if they works nor where to find them in OT, it's just build stuff actually.

plugin search directory:/home/dashie/.local/share/OpenToonz/OpenToonz 1.0/plugins
walkDirectory_: /home/dashie/.local/share/OpenToonz/OpenToonz 1.0/plugins
doLoad handle:(nil) path:/home/dashie/.local/share/OpenToonz/OpenToonz 1.0/plugins/DWANGO_BlurChromaticAberration.plugin
doLoad handle:(nil) path:/home/dashie/.local/share/OpenToonz/OpenToonz 1.0/plugins/DWANGO_BlurConvolution.plugin
doLoad handle:(nil) path:/home/dashie/.local/share/OpenToonz/OpenToonz 1.0/plugins/DWANGO_BlurCurlNoise.plugin
doLoad handle:(nil) path:/home/dashie/.local/share/OpenToonz/OpenToonz 1.0/plugins/DWANGO_BlurMaskedC.plugin
doLoad handle:(nil) path:/home/dashie/.local/share/OpenToonz/OpenToonz 1.0/plugins/DWANGO_BlurMaskedD.plugin
doLoad handle:(nil) path:/home/dashie/.local/share/OpenToonz/OpenToonz 1.0/plugins/DWANGO_BlurMaskedR.plugin
doLoad handle:(nil) path:/home/dashie/.local/share/OpenToonz/OpenToonz 1.0/plugins/DWANGO_CoherentNoise.plugin
doLoad handle:(nil) path:/home/dashie/.local/share/OpenToonz/OpenToonz 1.0/plugins/DWANGO_ComposeAdd.plugin
doLoad handle:(nil) path:/home/dashie/.local/share/OpenToonz/OpenToonz 1.0/plugins/DWANGO_ComposeMul.plugin
doLoad handle:(nil) path:/home/dashie/.local/share/OpenToonz/OpenToonz 1.0/plugins/DWANGO_ComposeOptical.plugin
doLoad handle:(nil) path:/home/dashie/.local/share/OpenToonz/OpenToonz 1.0/plugins/DWANGO_Drip.plugin
doLoad handle:(nil) path:/home/dashie/.local/share/OpenToonz/OpenToonz 1.0/plugins/DWANGO_ImageQuilting.plugin
doLoad handle:(nil) path:/home/dashie/.local/share/OpenToonz/OpenToonz 1.0/plugins/DWANGO_Kaleidoscope.plugin
doLoad handle:(nil) path:/home/dashie/.local/share/OpenToonz/OpenToonz 1.0/plugins/DWANGO_LightBloom.plugin
doLoad handle:(nil) path:/home/dashie/.local/share/OpenToonz/OpenToonz 1.0/plugins/DWANGO_LightGlare.plugin
doLoad handle:(nil) path:/home/dashie/.local/share/OpenToonz/OpenToonz 1.0/plugins/DWANGO_LightIncident.plugin
doLoad handle:(nil) path:/home/dashie/.local/share/OpenToonz/OpenToonz 1.0/plugins/DWANGO_Paraffin.plugin
doLoad handle:(nil) path:/home/dashie/.local/share/OpenToonz/OpenToonz 1.0/plugins/DWANGO_PencilHatching.plugin
doLoad handle:(nil) path:/home/dashie/.local/share/OpenToonz/OpenToonz 1.0/plugins/DWANGO_Tiling.plugin
doLoad handle:(nil) path:/home/dashie/.local/share/OpenToonz/OpenToonz 1.0/plugins/DWANGO_WaveGlass.plugin
===== PluginLoadController::finished() =====