Rework build process

Solves #2 (closed)

packages/desktop/Aegisub.desktop

+[Desktop Entry]
+Version=1.0
+Type=Application
+Name=Aegisub
+Icon=aegisub
+GenericName=Subtitle Editor
+Comment=Create and edit subtitles for film and videos.
+Keywords=subtitles;video;audio;text
+Terminal=false
+Categories=AudioVideo;AudioVideoEditing;
+MimeType=application/x-srt;text/plain;text/x-ass;text/x-microdvd;text/x-ssa;
+StartupNotify=true
+Exec=aegisub