In bld.sh the TiddlyWiki5 repo in the sibling directory is cp with npm install ../TiddlyWiki5, this creates a symbolic link.
This symbolic link is than cp to source/tiddlywiki, this is still OK.
Than the symbolic link in source/tiddlywiki is cp with -R source/* output/linux64/TiddlyDesktop-linux64-v0.0.13, here the link is broken, hence cp with -RH command to preserve the code.
You need to preserve the code if you move the build around.
Hope this makes it clear.
There is a small typo in the image that is used to show on the panel, the name is app-icon.png, in the the code it is used as app_icon.png, this results in a grey smudge instead of the black cat on yellow background.